In QLab 5, you just change the device an output route sends to, in Settings/Video/Output Routing
This has 2 advantages
You don't have to edit all your cues.
If you use a display with a different resolution, the output route will be scaled up or down to the new display size. This means that you could have multiple stages sending to an output route, and all the relative positions of those stages would stay the same on a display, whatever the resolution of the output display device!
Screen recording attached
Mic