I've been trying to use User Rename Lists, but neither this:
genre:=Pop:=Pop/Rock
genre:=Rock:=Pop/Rock

nor that seem to work:
genre:=Pop/Rock:=Pop

When I use mConnect HD and browse by Genre, they are still all there:
Pop
Rock
Pop/Rock

Am I missing something obvious?

I am running Asset UPnP R7.1beta 2 (but had the problem already with R7).