FWIW, even though it certainly wasn't that used, the Windows 'Mixed' Reality offering has this today. Specifically, it has great support for just bringing up as

FWIW, even though it certainly wasn't that used, the Windows 'Mixed' Reality offering has this today. Specifically, it has great support for just bringing up as many windows to apps as you'd like (I believe this was one of the cases for UWP), though I think the limit for active windows is 5-6. Firing up a few copies of Token2Shell for SSH was...liberating, especially when I could resize them on the fly. Plus, as it was in the virtual home environment, you could setup various 'workstations' and use them for different window configurations that doubled as decoration. The one thing WMR gets wrong is the blasted pop-up keyboard that you couldn't turn off (even explicit use of 'desktop mode'). While a lot of the stuff on Simula One's website is a bit fluffy (10x immersion? Really?), I hope it continues to get refined.