This add on is very close to how the original Firefox Tab Groups (Panorama) was. The one major feature it's missing is the lack of a "create new Group" option in the "Send To Group" tab context menu item. Currently the send to group context menu item only shows already existing groups and a option to refresh groups, if the Dev adds the "create new group" function then along with Firefox's new multi tab group selecting, we could shift select multiple tabs and then right click and create a new tab group out of them instantly.