Given the poor state FF API has been in ever since Quantum, this is as good a replacement for Tab Groups as can be expected. There is a rather unfortunate and extremely annoying issue where when you switch to a different group, your current tab moves to the new group, but otherwise it seems to work more or less as well as you could expect. I wish there was an option to close the "group management" tab when you select a tab in it, the way group management worked in tab groups.