Greetings!
I think since Rhino 6 it is possible to apply materials per Sub-object, in other words, applying different materials to different faces of the same polysurface, using the Ctrl+Shift select face, and then changing the material through the “Material” tab, in the Properties Panel. This works even for V-Ray materials, but only through this method, with the Properties panel. Currently you can’t do this through the Asset Editor.
Is it a techinical thing, or is it possible? This would smooth a little bit the workflow.