I think this is a great replacement for Tab Groups (the original Firefox version that was deprecated and the great add-on by Quicksaver that has gone extinct).

I wish we could click to drop down the icon on the toolbar to switch between named groups like we could in the Quicksaver version. The ability to save the entire set dynamically (without having to import and export) and switch between them like with Session Manager would be awesome as well.

The context menus are great and have a lot of options for grabbing sets of tabs to add to the list.

I did not use this add-on in FF56, so I can't speak to the upgrade path, but it seems as though they have instructions to follow for downgrading.