Thank you both, kind of fixed now! Even though some of these answers are redundant now, I’ll give you some more details; it might help with my next question: The mesh wasn’t visible in the game at all; it’s not a placeable item, just an asset in the environment; by composite mesh I do mean adding multiple meshes as components to form one main mesh; no animations are used; textures are from the game’s own files, and adding the new mesh to the mods folder did the trick.
But how can I make the composite mesh cook with the sublevel that is using it, so that others using the mod wouldn’t have to manually add the mesh to their folders?