how should i create lightmap uvs for my assets? can i create uv2 from uv without destroying uv. Or should i export output of hda to unity and use unity to create lightmaps. in which case how do i export it as a model, not just mesh. If i export as a model that contains mesh there is model import menu that allows me to create lightmaps uv. by default hda exports only mesh which doesnt have this option.

I dont want to use fbx rop, because i want to be able to automatically export and update many meshes and colliders every time i change my asset. since i use it to create models specificaly tailored to my level geometry