The first time I've used the extension, I tried to create empty tab groups, I clicked one, and instead of having the group tab openend in a new window, I've lost all the current tabs I had in my window!!! I was very angry. Please, add warnings, or something, and make things more intuitive. I don't like this behaviour. Opening a group should warns about the other tabs being lost, or letting the option to open in a new window, or opening the new tabs next to the old tabs.
Please add favicons and improve the tab menu, adding for instance a folder icon, or a different color when it's the name of a group of table. Things are not very readable and eye-candy like it is.