>>each tab can be in a single parent browser window or dragged off into its own browser parent window ! ... Maybe I don’t understand the problem scenario?
Can these separate tabs then behave like an interactive Windows app - e.g. drag an item to a higher sequence position on one tab and 2 other tabs instantly update to reflect the change?
Back when we had to make decisions, the answer was (or became) "no" because you don't want the dodgy site somebody happened to click while searching for "bicycle" to pull sneaky tricks to interact with the banking app on another tab, which was the exact example given at the time. Maye they overcame that since.
"... They ne'er cared for us
yet: suffer us to famish, and their store-houses
crammed with grain; make edicts for usury, to
support usurers; repeal daily any wholesome act
established against the rich, and provide more
piercing statutes daily, to chain up and restrain
the poor. If the wars eat us not up, they will; and
there's all the love they bear us."
-- Shakespeare: Coriolanus, Act 1, scene 1