[Sharlikran]

I would think nobody can be sure as to why that is because the functions and the API do only what is approved. Meaning we don't have explicit documentation for what will and won't work. So this is unfortunately the best answer I'm afraid.

If you do that and you are certain your spelling and path is correct, if you reloaded the UI, and if you existed the game and logged in with the mod active and they still will not change then it is not permitted to change them. You can try deleting the ShaderCache.cooked file and try again.

I see a lot of AVA textures and I have my doubts about being allowed to change any of that. The reason I feel you have to accept a "just because" answer is for the simple fact that code can not be prejudice toward only certain operations unless there are restrictions.