Nice legacy Tab Groups replacement on quantum! Most of hotkeys for switching groups can almost recover the legacy one except those limitation in extensions (That's no choice). Good to see this release just before legacy Firefox ESR end of support. Thanks for bringing the final hope and allow for move on quantum seamlessly.

I am looking forward to the free arrange be implemented and that will be fully replace, and/or even enhance of legacy Tab Groups.

Suggestion: Is it possible close the "Manage Groups" tab after switching groups? Otherwise whenever using hotkey to open "Manage Groups", it will switch back to the group with "Manage Groups" tab. The current solution is uncheck 'Open "Manage Groups" in new tab'.

Edit: already in STG 3.0.7, not experimental
Edit 2: Thanks for response. One more suggestion: how about close "Manage Groups" tab when it is inactive OR hide all other tabs when "Manage Groups" is active (so user must choose a group or close it to remain in current group)? This can force the "Manage Groups" tab never belongs to any groups, which prevent group auto switching when opening "Manage Groups".