alt Hacker News> So realistically no application did this.
Old versions of GIMP (back when the toolbars etc. were separate windows) used to let you move any of its windows to a different X screen. And by "move" I don't mean drag - there was a menu where you could select the screen to move to.
I really miss the tear-off-into-their-own-window menus. They were so handy.
I have to wonder if the fact that Wayland either never had or has only very recently gotten support for applications that need to place their windows at application-commanded locations on the screen meant that those lovely tear-off menus had to die.