I did this on patch 8. You need to download the BG3 Mod Manager and script extender.
You can get mod manager here :
https://github.com/LaughingLeader/BG3ModManager?tab=readme-ov-fileWhen you launch BG3MM you'll see a "tools" menu item which allows you to download & install script extender.
When that's done you need to go in BG3MM Settings menu , click on "preferences". It opens a dialogue window with several tabs. You need to go in the "script extender" tab and find a checkbox to "create console" which you must check.
Launch the game and a "console" window will show, spewing some output. Let the game load completely, then focus on the console and type the following commands :
-> If Wyll is already transformed and you want him to go back, type :
Osi.RemoveTransforms("S_Player_Wyll_c774d764-4a17-48dc-b470-32ace9ce447d")
-> To avoid the transformation occurring later, type:
Ext.Entity.Get("S_Player_Wyll_c774d764-4a17-48dc-b470-32ace9ce447d").CharacterCreationStats.BodyType= 1
(I got the info from the discussion in nexus mod "Wylla" because I'm using this to get a feminine Wyll and then had to resculpt her with the companionsedit mod, which doesn't work with the horns. So, this proicedure worked for me. You can find more details in these discussions.
https://www.nexusmods.com/baldursgate3/mods/2565?tab=posts)
Afterwardss you can uncheck the "show console window" in BG3MM preferences again, so it won't show up anymore when you launch the game.
This is my "Wylla" this is after the transform, with horns removed. I'm not sure if this image can be hotlinked. Just trying.
PS : This is only for PC's of course.