I think supporting such configurations is must have for a lot of users, especially the one who are coming from OS X or any tiling window managers(sway/i3wm). 

I like to have web browser(with documentation or something else) and multiple communicators(on multiple workspaces) on one monitor, and couple of workspaces(virtual desktops) with IDE, terminals, etc. on another monitor, but such setup is just impossible to get on kwin, I can pin the web browser window to all virtual desktops, but that is not working in the couple of situations when i need to use the first display for something else.