Reunwrapping a mesh after editing, when I've arranged the islands already

Hi, I’ve UV unwrapped a model and arranged the islands in a way that make sense for texture painting in Photoshop. Now I realize I have to edit the mesh. How do I unwrap again after editing without ruining my arrangement?

Thanks in advance

Pin the correct UV’s in place, that keeps them put while unwrapping.

Oh yeah, I forgot! Thanks!!