I also have Stage Manager off for now, but I know one circumstance in which it will be handy. I have an external monitor attached to my MBP (see profile for details). On that external I have five open windows that are open all the time. Those five apps are in my login items to start every time I login. Works well when at my desk and have the second monitor. However, I do travel, and I take my MBP with me. Booting and logging in on the road is a bit of a PITA as those same five apps open, but all on my MBP screen, overlapping and blocking each other. But I like having them available, so I end up minimizing them to the Doc, where they are forgotten. SM will let me park them "off stage" where they will not clutter the desktop, but not be forgotten, as they tend to be on the Dock. I'm not planning on traveling again soon, but I can imagine how it would work well.