Allow to add/assign custom materials per mesh after file load

By default Substance Painter only allows to have materials that are present e.g. in the source FBX file. It would be great however if there were a way to also allow the user to assign a new/custom material to specific meshes so that if e.g. an Alembic is loaded with multiple meshes and there only being a single "DefaultMaterial" entry that the user has the ability to split it into multiple materials directly in Substance Painter.