Recently I wanted to play with iframes at https://www.drawpad.org/multi.html (useful for reference for what I’d like to see) but ran into issues with cross-origin tags (on this site included). I think it’d be interesting if we could have tabs arranged in groups that we could view and then possibly click on to enlarge. It would be a more unique approach to the issue of multiple tabs, and if these multi-tabs acted as a single tab in the overall bar, I would find that insanely productive.
There are many sites I like to keep open just to know when a change occurs (message received or reply posted) but most cause issues with login or cross-origin and so the only solution I can conceive of is browser side with the tabs. If these multi-tabs could still give alerts to the user (as this forum and facebook do) they would be an amazing selling point!