It is possible to give a weapon the use effect of an item like a vulnerary or pure water, but in-game it shows grayed-out use text. Is there a way to make this work?
There’s an unfortunate number of moving parts to usable items, but yes; it’s plenty doable.
The most likely culprit is that the game’s first check for if an item is usable is if its item ID is at least some rather high value (the initial location of the staves or vulnerary, i forget which). Regardless of what edit setup you’re using, there should be some manner of “essential fix” in the Skill System repository that notes this; or in FEBuilder’s searchable patch list.
You have to give the weapon both a valid “Use Effect” byte in the item editor, and also tell it to have an “Item Effect” which is a separate section, I believe called
Item use effect in most places?