This is very useful for power user, or even one who want to separate some tabs into individual zone/segment. Eg. right tabs for social media and emails, left tabs for work related, top tabs for casual/once-off page browsing, maybe bottom for banks, financials, etc.
I think this makes sense nowadays in the era of ultrawide and big screen monitor.
Bringing the idea further or sideways, since multi-monitor setup is very common now, maybe the ability to have multi-window browser with each saved tabs would be good too. So say, having one window with many tabs relating to work on left side of an ultrawide monitor, and another group of tabs on another window on the right side of the ultrawide, then another window on second monitor with another group of tabs and these states and tabs are saved persistently so that restart or closing the browser would not be a problem and still start the next day with the same setup, now that would be a banger.
Hopefully these two ideas are considered and implemented.