Helium314
Looks like shops mapped as relations are not displayed in most renderers, none of the indoor renderes linked in https://wiki.openstreetmap.org/wiki/Indoor_Mapping#Austria.

I suspect this is because OSM wiki entry for shop inidcates that the shop key should not be used on relations.

A possible solution would be to add a shop node and put it in a relation with the used rooms. But this seems like a bad workaround...