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So I am just figuring out how to work with textures, back then I just overwrote existing ones... the thing is if I import a texture into the file and move it between p_start and p_end (right?), then right click > graphic > add to patch table, then the entry gets created but it says "In archive: (!) NOT FOUND". However, if I do it this way it works: open texture editor -> new from file. Why does it not work the other way?

Adding to patch table will not create a texture. It will just add to the list of patches that can be used to create a texture. You want "add to textures".

*facepalm* thanks <3