Just UV import is what I want. Because my subtools is some hair mesh, I have tried normal way to import lowpoly then projection, some detail of mesh and polypaint will lose. So can I just import UV for subtools?
If you import an OBJ and only the UVs have changed, then the UVs should update automatically without any error messages.
If the vertices are in different ppositions and you don’t want the mesh to update to reflect this, you could store a Morph Target first. Then you can load in the new UVs, and then switch back to the old morph target.
If the vertex order is different however, then you wont have much luck transferring UVs and so a projection is most likely needed.