Thank you for the feedback - this is exactly the kind of thing I'm looking for. You have to drag the icons from finder, not from the dock. Does that work?

Yeah, that worked! Could you see if you could get it to work with dragging from the dock? Also, when you switch groups, I didn't realize it "exits" all of your other apps. It may be a good idea to just hide the other apps. Thoughts?

I think dragging from the dock always just removes the apps from the dock. At least that's the default behavior, and I have not found a way around it.

Cool!

Lots of people are also suggesting hiding the other apps. I might try to implement this as an option, but what I'm going for is de-cluttering the command-tab app switcher, and I don't think hiding the apps will achieve that. However, this feedback is inspiring me to see if it's possible to hack the task list, or whatever it's called.