Walls need to show in a multi-category schedule. Everything else, including the kitchen sink does, but walls do not. System Panels show in them. If a system panel can show, a system family wall should as well.

What would be even cooler, as I continue dreaming, would be the ability to select what categories a mutli-category schedule could contain, rather than having to filter things out. It would stand to reason that you could add a drop-down menu to allow mutliple selection of categories? I dunno. Cheers!