Here's an update on progress. This is not pushed to GitHub yet, but I'll do so in the next few days.
I've figured out how to integrate with KiCad frame, and I think it looks great! There are still a few tweaks to make, and I'm not super happy with the buttons, but they are functional.
Click on the graphic to see the LayerViewSet control panel on the bottom:
A note on integration: it doesn't integrate with the Layer Manager, but only with the KiCad frame. This means it doesn't float around with the Layer Manager when you decouple the Layer Manager from the KiCad frame. Ideally, LayerViewSet would move around and float with the Layer Manager itself, but I haven't figured that out yet.
And I'm still working on tweaking the title bar. Not sure of the right combination to make it work similarly to "Visibles".
The "Click on any label." is where message text will go to indicate progress (if any messages are needed, otherwise I'll remove it)