Most settings in this mod are available to modify via both the MCM and the Spellcrafting Journal item, whichever you prefer.  This article lists all global variables that correspond to mod settings.  If you'd like to set a variable to a value outside of the MCM range, or the variable you want isn't available in the menu, perhaps this list will help.

To change a global variable value, you can run in the console:
set aaSimpleVarVariableName to 0

To see the current value of a particular variable, you can run:
help "aaSimpleVarVariableName"
To see the current value of all variables associated with this mod, you can run:
help "aaSimpleVar"
(Why "aaSimpleVar"?  The original working name of this mod was something along the lines of Simple Spellmaking or Simple Spellcrafting, and so most of the Editor IDs are prefixed with that.  After a few months of working on the mod, it had grown in scope and I was forced to conclude that the system was no longer very simple, so I renamed it.)

Virtually every setting may be modified mid-game; if you need to do something extra for a setting to take effect, I've specifically called it out below.  Let me know if I missed any!

Variables are listed as:
aaSimpleVarVariableName [default value] - Explanation of variable function.

aaSimpleVarActualMagickaCompose [0] - Set to 1 to check that your character is capable of casting a spell before allowing you to discover it.  Requires SKSE.
aaSimpleVarActualMagickaCraft [0] - Set to 1 to base crafting costs on actual spell cost for your character.  Requires SKSE.
aaSimpleVarAllowCompose [1] - Set to 0 to disable composing spells from scratch.
aaSimpleVarAllowCraft [3] - Set to 0 to disable all crafting; 1 to allow scrolls only; 2 to allow staves only; and 3 to allow both.
aaSimpleVarAllowJournalGrimoire [0] - Set to 1 to allow using the Spellcrafting Journal as a grimoire (to store spells).
aaSimpleVarAllowReverse [3] - Set to 0 to disable all reverse-engineering; 1 to allow scrolls only; 2 to allow staves only; and 3 to allow both.
aaSimpleVarAlwaysSucceed [0] - Set to 1 to skip chance roll and always succeed on an attempt to compose a spell.
aaSimpleVarAlwaysSucceedNotes [0] - Set to 1 to skip chance roll and always succeed on an attempt to write spellcrafting notes.
aaSimpleVarAlwaysSucceedReverse [0] - Set to 1 to skip chance roll and always succeed on an attempt to reverse-engineer a scroll or staff.
aaSimpleVarAncientTextChanceNone [0] - From 0 to 100, the relative percent chance of not seeing an Ancient Text spawn when one could be spawned.  Put another way, setting this to 75 means that Ancient Texts are only 25% as likely to spawn, so they will be four times rarer.  (Even if set to 0, for a 100% relative chance, they will not always spawn from their possible sources.)  This setting only matters if you have the Ancient Text add-on.  Will likely take a few in-game days to take effect for vendors.
aaSimpleVarAncientTextSpellChance [1.0] - From 0.0 to 1.0, the relative chance of getting a spell from an Ancient Text.  If set to 0.0, you will never learn a spell and will instead always get some number of notes when translating a text.
aaSimpleVarAnimFurniture [0] - Set to 1 to play animations when using furniture.
aaSimpleVarAnimOn [0] - Set to 1 to play animations when using journal / lesser power.
aaSimpleVarAutoSaveLoad [1] - Attempt to auto-load and auto-save settings from xml with FISSES when opening and closing the MCM.  If you don't have the FISSES add-on installed, this setting should not affect anything.
aaSimpleVarSwapCamera [0] - Set to 1 to swap to third person and then back to first person when playing an animation.  I recommend only using this if you normally play in first person; otherwise, you'll be swapped into first person at the end of the animation anyway.
aaSimpleVarBaseChance [0.4] - From 0.0 to 1.0, the base chance of success in research when you could normally get spells of that level from a vendor (e.g. level 65 for expert spells).
aaSimpleVarBasePromotionChance [0.01] - From 0.0 to 1.0, the base chance of success in research when you have just gotten to buy spells of the previous level (e.g. level 40 for expert spells).  You'll see weird behavior if you set this value to higher than the base chance.
aaSimpleVarBonusChance [1.0] - Multiplier to relative bonus chance for extra magicka above the research / etc cost.  Meant to mostly be a tedium reducer for higher-level characters on spells that you already have a decent chance to discover; see the example graph in the mod images for how this impacts chances at different skill levels.  Set to 0.0 to ignore your magicka when calculating chances.
aaSimpleVarChanceMax [1.0] - From 0.0 to 1.0, a cap on success chance.  For example, setting to 0.95 means you will always have at least a 1/20 failure chance for any action no matter how skilled you are.
aaSimpleVarChanceMin [0.0] - From 0.0 to 1.0, a lower bound on success chance.  For example, setting to 0.05 means you will always have at least a 1/20 success chance for any action no matter how unskilled you are.
aaSimpleVarCheckMasterQuests [0] - Set to 1 to only allow composing master-level spells if you have completed the relevant quest.  This option actually checks the global variable used to control whether college vendors will sell master-level tomes, so it's possible if you have a mod that changes how master tomes are sold that this feature won't work correctly.
aaSimpleVarCooldownFloor [0.0] - The limit to how much cooldown from researching spells can affect your base chance in composing.  By default, composing can become near-impossible for higher-level spells; increasing this value will lighten the impact and setting to 1.0 will prevent cooldown from affecting your research chances.
aaSimpleVarCooldownPenaltyScale [0.0] - How strongly researching spells can impact your chances.  By default, this feature is off (success chance is unaffected by having composed a spell recently); if set to 1.0, base chance will be multiplied by aaSimpleVarCooldownFloor after successfully composing one spell.
aaSimpleVarCooldownRestorePerHour [1.0] - How much of the cooldown factor is restored per hour spent doing anything except composing spells, writing notes, etc with this mod.  If set to 1.0, your chances will always recover to normal after an hour.  If set lower, this can take longer.
aaSimpleVarCostMultScroll [0.0] - Scale paper and ink costs for scroll crafting such that the materials spent will cost approximately this fraction of the value of the scroll produced.  For example, in vanilla, a scroll of Fireball is worth 100 gold; a roll of paper is worth 4 gold; and an inkwell is worth 1 gold.  With default settings otherwise, a value of 0.25 for this setting will mean this scroll requires 6 paper and 3 ink to produce (27 gold).
aaSimpleVarCostMultTome [0.0] - Scale paper and ink costs for tome crafting such that the materials spent will cost approximately this fraction of the value of the scroll produced.
aaSimpleVarDisableAdvancedSearch [0] - if set to 1, faster search functions using array.Find will not be used and a slower legacy search will be used instead.  May be useful if you're on a particularly old version of Skyrim.
aaSimpleVarEnchCompareSKSE [0] - Set to 1 to check the enchantment of a staff against known staves when reverse-engineering.  This allows reverse-engineering of staves that aren't the default type (for example Forsworn or Falmer staves), but may increase search times.  Requires SKSE.
aaSimpleVarEnchExpMult [1.0] - Multiplier to enchanting experience from crafting staves etc.  Set to 0.0 if you don't want to get enchanting experience from this mod.
aaSimpleVarEquipSpell [1] - By default, this mod will equip a spell in your right hand when learning it.  Set to 0 if you don't want this mod to change what you have equipped.  (Automatic spell learning will never change what you have equipped, as this frequently happens during battle and it would probably be annoying!)
aaSimpleVarFadeToBlack [1] - Set to 0 to turn off the fade-to-black effect when passing time.  This setting doesn't matter if you don't have the mod set to pass time when composing or crafting.
aaSimpleVarFurnitureBookChanceNone [0] - From 0 to 100, the relative percent chance of not seeing a furniture book ("Primer on Spellcrafting") when it's possible for one to spawn.  Set to 100 to never see this book in leveled lists.  Will likely take a few in-game days to take effect.
aaSimpleVarFurnitureGemScale [1.0] - A multiplier for the visible size of gems on the Spellcrafting Escritoire.  Won't affect furniture already placed if you change this setting mid-game; please pick up and re-place them to apply the scale.
aaSimpleVarFurnitureHideLights [0] - Set to 1 to disable lights used by furniture.  Will likely require picking up and re-placing the Imbuing Lab for this to affect it correctly.
aaSimpleVarFurnitureRecipes [0] - Set to 1 to enable furniture recipes regardless of whether you have a copy of the Primer on Spellcrafting book.  You may also wish to set aaSimpleVarFurnitureBookChanceNone to 100 to reduce vendor clutter.
aaSimpleVarFurnitureSnapAngle [15.0] - Angle in degrees to rotate by or snap to when placing furniture.  If set to 0.0, furniture can't be rotated after being placed, but will be placed at exactly the same angle the player is standing.
aaSimpleVarFurnitureSnapPos [8.0] - Distance in game units to translate furniture by or snap to when placing furniture.  If set to 0.0, furniture can't be translated after being placed, but will be placed exactly in front of the player.
aaSimpleVarFurnitureSuppressEffects [0] - Set to 1 to disable explosions shown by furniture when reverse-engineering and composing.
aaSimpleVarGiveBooks [0] - Set to 1 to add spell tomes to the player's inventory instead of adding spells directly.  May be desirable if you have a mod like Immersive Spell Learning!
aaSimpleVarGrimoireAllSpells [0] - Set to 1 to automatically add spells learned by research to the grimoire.  May help this mod work better alongside other mods that add a mechanism for forgetting spells (so you won't re-learn spells removed by those methods when researching with this mod).
aaSimpleVarInitDoExplicitCopy [0] - if set to 1, initialization will use older code that is slower for additive patches.  May help if you're seeing a strange initialization issue; please let me know if you run into this.
aaSimpleVarInitNoParallel [0] - if set to 1, initialization will not do any work concurrently, which is expected to be at least several times slower for most users.  May help if you're seeing a strange initialization issue; please let me know if you run into this.
aaSimpleVarInkCost [1] - Number of inkwells consumed when writing notes.
aaSimpleVarInsightCrossover [0.25] - Base at-level automatic spell learning chance.  Increasing this will make it easier to automatically learn higher-level spells around the time when you could have gotten them from a spell vendor.  Automatic spell learning is already relatively harder for higher-level spells; this variable can be changed at any time and will take effect immediately, so feel free to play around with it and let me know if you think a balance change is needed!
aaSimpleVarInsightFailRetainFraction [0.9] - the fraction of the internal progress counter retained if the mod is ready to try to teach you a spell but doesn't recognize the spell you're casting. Can be set between 0.0 and 1.0. Higher values for this make automatic spell learning more consistent if you use shouts regularly and/or have spell packs that aren't patched into this mod.
aaSimpleVarInsightInterval [100.0] - Multiplier for the amount of spellcasting needed in between rolls to see if you can automatically learn a spell.  Increase this to learn spells less often.  Setting to 0.0 may be helpful to test the feature (as it will attempt to teach you a spell near-constantly as you cast).
aaSimpleVarInsightMode [0] - By default, you learn spells as you hit the threshold, no matter what you are doing at the time.  If you have many other scripts running actively during combat, you may find that this adds significant script lag.  Set to 1 to keep an internal record of how much you have cast spells and try to teach a spell upon changing locations or sleeping instead.
aaSimpleVarJournalHideConfigure [0] - Disable the "Configure" option when opening the Spellcrafting Journal.
aaSimpleVarJournalRecipe [1] - Set to 0 to hide the Spellcrafting Journal recipe.
aaSimpleVarLearnQuestSpells [0] - Set to 1 to allow learning spells that are in the 'exclude from normal discovery' category, such as Flaming Familiar and Soul Cairn summon spells in the pre-made patches.  If you're using the automatic spell learning feature, you may need to remove and re-add the perk via the MCM or journal for this setting to take effect.
aaSimpleVarLevelBase [50] - 'Base' value used for scaling impact of spell level on magicka costs.  Increasing this value makes the difference between novice and expert spells less.  If you set to 0 you will see some weird behavior.  This setting may be easier to modify using the MCM or journal menu.
aaSimpleVarLevelRestrict [2] - Set to 0 to only compose spells that exactly match the requested level.  Set to 1 to compose a spell of any level up to the requested one randomly.  Set to 2 to attempt to compose a spell at the requested level and fall back to lower-level spells if none exists.
aaSimpleVarLoseMaterials [1] - By default you'll lose ink and paper anyway if you try and fail to compose spellcrafting notes.  Set to 0 to only lose magicka instead.
aaSimpleVarLoseMaterialsNotes [0] - By default you lose only magicka if you try and fail to compose a spell.  Set to 1 to lose spellcrafting notes as well.
aaSimpleVarMagicMult [1.0] - Multiplier for all magicka costs.
aaSimpleVarMagicMultCraftScroll [1.5] - Relative cost of crafting a scroll (vs composing that spell).
aaSimpleVarMagicMultCraftTome [0.75] - Relative cost of crafting a tome (vs composing that spell).
aaSimpleVarPaperCost [2] - Number of rolls of paper consumed when writing notes.
aaSimpleVarPassTime [0.0] - Multiplier to amount of time to pass when researching a spell.  Default is 0.0 to pass no time.  If you have another mod that updates something every so often in game time, such as some survival mods, please test this to make sure it works together ok!
aaSimpleVarPassTimeCraft [0.0] - Multiplier to amount of time to pass when crafting an item.  Default is 0.0 to pass no time.  Again, please test this if you have mods that might interact!
aaSimpleVarScaleWithMod [1] - By default this mod attempts to take Fortify Skill effects into account when calculating magicka costs.  Set to 0 to ignore ActorValues like DestructionMod; this may help if you have another mod that changes how Fortify Skill effects work and you're seeing strange behavior.
aaSimpleVarScaleWithPowerMod [1] - Same as above, but with DestructionPowerMod.
aaSimpleVarSetBooksRead [0] - Set to 1 to mark books read when learning their spells by research.  If you don't have Papyrus Extender, this option won't function.
aaSimpleVarSkillBase [100] - 'Base' value used for scaling impact of skill level on magicka costs.  Increasing this value makes the difference between 0 and 100 skill level in a school of magic less.  If you set to 0 you will see some weird behavior.  This setting may be easier to modify using the MCM or journal menu.
aaSimpleVarSkillMax [100] - Maximum chance of success is reached at this skill level in each school.  If you have an uncapper (or want to increase the difficulty), you may wish to increase this value.
aaSimpleVarSpellExpMult [1.0] - Multiplier for magic school skill experience from research etc.  Set to 0.0 if you don't want to gain experience in any school of magic when researching.
aaSimpleVarTimeBase [50] - 'Base' value used for scaling impact of skill level on time passed.  Increasing this value makes the difference between 0 and 100 skill level in a school of magic more.  If you set this above 100 and use an uncapper it's possible to see weird behavior.  This setting may be easier to modify using the MCM or journal menu.
aaSimpleVarTutorial [1] - Set to 0 to suppress all tutorial messages shown by the furniture.  If you have this setting at 0 and want to see tutorial messages again, you may need to set both this setting and the appropriate one(s) of the three below AND place a new furniture item for those messages to show.
aaSimpleVarTutorialGrimoire [1] - Set to 0 to suppress tutorial messages specifically from the grimoire furniture.
aaSimpleVarTutorialImbuingLab [1] - Set to 0 to suppress tutorial messages specifically from the imbuing lab furniture.
aaSimpleVarTutorialWritingDesk [1] - Set to 0 to suppress tutorial messages specifically from the writing desk furniture.
aaSimpleVarUseTrance [1] - Set to 0 to access menu-style spell composition from the Spellcrafting Journal instead of the Spellcrafting Trance lesser power.  If you have this set to 0 and want to swap back to using the trance, you may need to read the journal again to add the trance power to your character.
aaSimpleVarVerbose [1] - Set to 0 to show fewer messages when using the mod's features (for example, hide the messages for ink and paper items consumed when crafting notes).