The only way I know of to get modded items working mid-playthrough is by changing the meta.lsb of the unmodded savegame to the meta.lsb of a modded (new) savegame, tricking the game into thinking that the mod is actually enabled.
I'm honestly not sure if the method still works though, since we developed it back when the MetaData was in a differently named file of the savegame.
Theoretically, you should be able to start a new game with a single mod enabled and save once. This creates a save folder in Documents/Larian Studios/.../(new save game)/. Copy the meta.lsb file in there, and move to your unmodded save. Paste the meta.lsb over to replace it, and hopefully when you start up the game the mod effects take place.
Be sure to backup your saves before doing any save editing though.
