Yeah, it doesn’t work in 4.0. It gives an error when you try to enable it in the preferences window. You can check here: TexTools for Blender - #970 by oo_1942 There is someone maintaining it and he mentioned the addon needs a full revision to work properly in 3.6 and especially 4.0. Maybe you can take a look and see if you could help?
I understand. The dev hasn’t worked on the addon in a long time if I am not mistaken. That feature I believe was how the addon was supposed to work but it doesn’t. I think adding something to a forked version wouldn’t be a bad idea but if you don’t want to. That’s okay.