This add-on is great but it does not 're-tab' the window once you exit fullscreen mode. More importantly, it does not give the user the choice to use the normal behavior of the fullscreen button which might be preferred in certain occasions (e.g. for short videos where you don't necessarily need to spawn a new window). Adding an on-off toggle button to the add-ons bar, together with a keyboard shortcut to fire it, will improve this useful extension quite a lot!!! (3 Stars)

EDIT 31/07/2019: Extension has been modified to support some of the above changes and has new very useful features :) Re-tabbing a fullscreen window is still a bit buggy (tested so far with YouTube), otherwise very useful extension!