I installed the add-on as a substitute for TabGroups. Initially it worked fine. Not quite as convenient as TabGroups was but absolutely fine for the start. But then all the groupings I created disappeared. Opening the overview showed 1 tabgroup and not a single tab. I deactivated the add-on and all my hidden tabs reappeared. After enabling the addon again (or deleting and installing it even), the overview does not open anymore. Neither clicking on it nor the shortcut do anything. I use the most recent version of FF (just check for updates). Once provided with a solution I will move up my review to 4 stars.

Great features to add would be the following: Going to a tab outside the current tab group by typing in the address bar = search mechanism, moving tabs more easily without needing to go into the overview,