Multi-tag with custom tag behaviour

[JoaBack]

I would like to have a "Format" tag that behaves like "Genre" with multiple values eg that you can have both the genre "Classical" and "Opera" and "Piano solo" and "Impressionist", in this case for example "Live recording" and "Box Set", and browse one after the other.

This doesn't work out of the box, is it because of Minimserver or the control point (android BubbleUpnp), or is it something I could configure somehow?