I have a 3-display setup where the 3rd display also runs a HDMI sound gateway. Sometimes the 3rd display is off, so I want to set it to replicate one of the other monitors. I can't disable it because then the HDMI output also gets disabled.
What I do manually and I'm looking for a way to achieve programatically is in the display settings GUI drag the 3rd monitor on top of one of the others so that it duplicates the display and windows can't get stuck on an invisible display. So basically I'm looking for something like a set-display-coords 3 0 0 / set-display-coords 3 3840 0 command.