Move windows between displays without dragging I'm using a 2011 iMac running MacOS Sierra with an HDMI output connected to a projector. When I want to watch a film on the projector, I just drag iTunes over to the second display and watch. If I forget to drag iTunes back, it ends up stuck on the other display. This is because the Mac still sees the second display when the projector is turned off. This means the only way to get iTunes back on the main iMac display is to turn the project back on so I can see the iTunes window and drag it back across to the main display. This also happens to any other app I "leave behind" on the external display and forget to drag back over. What I've tried:


Quitting and relaunching the app. This doesn't work, as MacOS remembers which display the app was on previously and re-launches it on that display
Finding the app in Mission Control. This doesn't work, because each display has its own Mission Control. I therefore can't see the spaces on the external display in order to grab the iTunes window and drag it to a space on the built-in display
Right-clicking the app icon in the dock and selecting "Show all windows". This just displays my wallpaper with a message in the centre saying "No available windows" (presumably because the window is on the external display).


I am hoping there's a key combination or some other trick to force the windows of the app to move over to the current display.
If you want a trick, you could briefly unplug the HDMI cable from the iMac. That should signal Mac OS that there is only one display and it will move all windows to the only remaining display.