[teddyh]

> Anyone remembering multi sub window apps in the Microsoft office suite in the 90s/00s

It was called MDI: <https://en.wikipedia.org/w/index.php?title=Multiple-document...>

[Propelloni]

Yes, and from day one Opera (when it was still called Multitorg) used it to give us something like "tabbed browsing". I think that was in the mid-1990s ;)