Fails to do what it alleges to do out of the gate by hiding tabs that cannot be easily reopened and not displaying the UI element it supposedly requires. If you do manage to reopen a grouped tab, it then hides all of the other tabs in your window.

I'm actually mainly a Vivaldi user, so for me personally that browser's tab grouping should be the baseline expectation, not whatever this is trying to do.

Just a very poor user experience all around.