I just logically group tabs into the same terminal window. All OS's have hotkeys for switching between tabs and windows.
seriously, a window manager that can group windows and manage those groups would be awesome. workspaces help, but they are often just there, and can't be managed, reordered, named, etc..
actually, i think kde may have some of that functionality.
i still prefer tmux in any case because it is more scriptable, and it provides a detach function. although i recently started exploring wezterm, which can be configured to work like tmux and also has a way to detach and reattach sessions: https://news.ycombinator.com/item?id=44762241