For people that care to learn something from my findings. This is what it all started with, finding out what everything does.
DogmeatNoVisualsOnRetrieve [KYWD:0007820B]
Objects dogmeat can retrieve, but will not appear in his mouth.
ma_armor_lining [KYWD:0007FACA]
Does nothing unless a mod uses it for something. Mostly removed in Meliora. Doesn't really matter if it's present.
ma_armor_Universal_Lining_Torso [KYWD:001833A3]
Adds different crafting options like lighter build. There is also leg and arm linings like this that do similar.
Armor_NoFirstTimeLoot [KYWD:0004F42C]
It's supposed to allow you to loot the underarmor. If this is missing, you can't pick it up. But it does nothing.
CA_ObjType_PrewarItem [KYWD:000A729B]
If an item is prewar NPC's will comment on it. Meliora adds this to every "pristine" item.
AnimHelmetCoversMouth [KYWD:001E5F73]
This is for headgear that covers the mouth. It turns mouth animation off for optimization purposes. Added on facegear that hides the mouth.
ArmorBodyPart... (eyes, hands, head, etc)
Does nothing unless a mod uses it for identifying. Meliora adds this to every piece that didn't have it.
usePowerArmorFrame...
Does not seem to do anything special. Some underarmors have it, some don't. They can all still use PA's. No clue.
FeaturedItem [KYWD:001B3FAC]
This causes the item pickup screen and "hell yeah" commentary to occur. Mostly removed since it's annoying. Silver shroud has it now.
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Here is some of the keyword stuff that changed in Meliora.
Keep in mind that I didn't make many notes on this. But the most important word for this is CONSISTENCY.
Removing keywords that were not needed, added keywords that are needed. Making sure every same piece of gear has the same useful keywords. Bethesda is very sloppy in that regard and nobody that I can tell has done this yet. ECO is pretty good with it but doesn't go as in-depth as Meliora goes.
Added ap_legendary attachpoints, so mods that do legendary transfers work out of the box with it. Available on everything except for facegear and non-combat headgear. This is done so you don't slap legendaries on every thing you wear. Some special headgear has it (like Ironsides hat or Pirate hat), I'm not going to list them, go find them.
Added ca_objtype_prewaritem to every prewar item so if you wear it, people comment on it.
Added vaultsuitkeyword to all the other Vault-Tec clothing so they comment about you coming from a vault, same as the Vault Suits. Removed this keyword from all other gear that should not have it.
Added ArmorTypeHelmet to every helmet so other mods can identify with it.
ArmorBodyPartHead is only added to headgear that also covers the face. Removed it from a bunch of headgear that should not have it.
Added ArmorBodyPartEyes to each pair of eyegear.
Added dn_Clothes to a bunch more items that didn't have it for icon mods & mods that change the INNR naming.
Removed Tutorial_DamageResistanceObject from every single piece of clothing and armor except for the Vault suits. This removes that stupid tutorial popup every single time you pick up a piece of clothing. Now it only does it on vault suits (the first clothing you pick up in the game).
Removed anim
A lot of this stuff is done so mods like ECO (Equipment & Crafting Overhaul) can make use of it. A lot of these keywords do nothing in a vanilla game.
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Bodyslots
[U] has been removed. It's useless.
Meliora does not do clipping, so [A] is in place wherever an armor piece will clip. Some armors have had all body slots removed. And there are some that have partial armor slots available.
46 Headband has been removed from all headgear. This makes gas masks and other full face gear work with all the headgear.
47 eyes, 48 beard & 49 mouth have been adjusted on a bunch of clothing and headgear to make them visible again. Some clipping might occur with the beard but it will be very minimal.
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Other changes
The resistances dtPhysical & dtElectrical are both "broken". Physical makes DR have funky values that make no sense. And electrical adds to ER resistance instead of it's own. In general, resistances are not that useful because Bethesda lazily implemented them.
added dn_clothes to almost every piece of clothing that should have it. Makes it work smoothly with mods that change it, like icon mods or ECO.