In the slab-specific tab the right-click info was there. That’s how I was quickly able to figure it out. Very easy fix so I’m only posting this as an FYI in case you’d prefer to include it in the next release, or for anyone who’s using the same tab as me and wondering how to get to the styles .
Thanks @keithscadservices ! Actually, that toolbar requires an update, not only for that missing Slab Styles command (or the roof styles too), but also because it should include many other commands available in other toolbars: