How it works
Spells that are cast on self and have a duration can be made toggleable. Cast a toggleable spell once to toggle it on, and the effect remains until you cast again or the spell otherwise ends (e.g. invisibility breaking when you attack).

You need to have enough magicka to cast the spell, but there's no initial cost. Instead while the spell is toggled on there's a cost to maintain it, reducing your magicka by an amount per second. This amount is the same as if you were to re-cast the spell when it would normally expire.

For example, if you have a spell that costs 100 magicka and lasts for 100 seconds, it will cost you 1 magicka per second to maintain. A spell that costs 100 magicka and lasts for 200 seconds costs 0.5 magicka per second, and so on.

You still regenerate magicka as usual, but if your maintenance costs are higher than your regeneration, your magicka will decrease until hitting 0, at which point all toggled spells will be dispelled.

Balance-wise the effect is that toggled spells make you no weaker or stronger than usual. They cost the same amount of magicka as if you were casting them upon expiration, and you'll benefit from all perks, enchantments, etc. that improve spell duration or cost.


Making spells toggleable
Spells can be made toggleable through the Spell Toggle MCM menu:

• Add Current Spell - Makes the spell currently in your right hand toggleable, if eligible.
• Add Spell - Lists out spells you know that can be made toggleable; select one to add it. Note that this menu is quite slow, so you'll have to wait a moment after clicking it for the list to come up.
• Re-add Default Toggleable Spells - If you have Form List Manipulator (FLM) installed some appropriate spells from the base game will automatically be made toggleable - Oakflesh, Flame Cloak, etc. This makes them all toggleable if you removed some, didn't initially have FLM installed, or added/changed FLM inis (see below).
• Toggleable Spells - Lists all spells that are toggleable. Click on one to remove it and restore the spell to its original behavior.
  

It's possible to make FLM inis for mod added spells so you don't have to re-add spells on each new game. Look at the included SpellToggle_FLM.ini for an example. I'm also happy to include FLM files for various mods if you send them to me.


Gameplay Notes
There's a huge variety of effects that you can make toggleable, far beyond the typical armor spells, especially if you're using mods that add new spells. Try things like invisibility, bound weapons, ethereal, healing, auras/cloaks, waterbreathing, resistances, speed buffs. All the buff or situational spells become so much more practical when you're not having to constantly cast them.

Some mod-added spells won't play nicely with being toggled, either because they're scripted for a specific duration or would be unbalanced. An example spell from Apocalypse that wouldn't be good for toggling:
"Sealed Resolve: Places a seal upon the caster for 15 seconds. Losing 50% of your current Health unlocks the seal, halving incoming damage for its remaining duration."

If a spell doesn't work well you can simply remove it from Toggleable Spells list.

Being limited to self cast spells means that most summons can't be toggled. However it should be possible to use a mod like Conjure Next To Caster to allow toggling summons.


Installation
Make sure you have the requirements installed: SKSE, SkyUI, Papyrus Extender, JContainers. Install as usual with your mod manager.

Form List Manipulator is optional but recommended.


Compatibility
SpellToggle.esp needs to load after any other mods that change the fDamagedMagickaRegenDelay game setting to something other than 0. I'm not aware of any, but please let me know if you encounter any so I can add a note here. MO2 will show the conflict in the Plugins tab.


There are a bunch of similar mods. What makes this one different?

• Perks, enchantments, etc. that increase spell duration are still useful. Your character is no weaker or stronger than before, aside from less time spent in casting animations.
• Properly handles dual casting, spells with multiple effects, spells that can end early, dispels, magicka loss.
• No patches needed.