Groupy seems to work well with other apps, but it’s not playing nicely with Scrivener. Or rather, it would be more fair to say that Scrivener’s not playing nicely with Groupy, specifically in regards to Quick Ref panels and Comp Mode.
There’s a long-time Windows Scriv bug, from beta days, where launching Comp Mode on the main editor will arbitrarily reposition open Quick Ref windows. Unfortunately, a side effect of this bug is that Groupy Quick Ref groupings are broken when Comp Mode is launched.
My workaround for the Scriv bug has been to enable Window > Float Quick Ref Panels. For whatever reason, when this is enabled, Comp Mode no longer repositions the Quick Ref windows. BUT, when I enable that setting, Groupy no longer allows me to group Quick Ref panels! 
A lose-lose situation.
So my Scrivener use case is broken. But I still might purchase Groupy, as tabbing Excel spreadsheets would be very handy. Thanks again, John, for the recommendation.
Best,
Jim