
I guess that's better than the PC behavior where even if you switch the source on the display back to the Mac, Windows still thinks its connected and continues to extend the display (the fix for that is to go to display properties and select "only show on display 2") , but thats a whole other gripe. I then have to move everything back to the big display.

The application all stay on the laptop screen and the big screen is empty when I switch the source back on the monitor. Prior to macOS Big Sur, if I switched to the PC input on the monitor, all the macOS windows would shift over to the built-in laptop display, and then shift back to their correct window once I switched back. Step 1: Begin by opening two or more windows that you want to be paired in a split-screen layout: Browser windows, apps, documents whatever you want. Each computer also has its own dedicated monitor (built-in for my Macbook, an old external for my PC). I switch between the two sources on the monitor depending on what I'm doing. I have one big 4K monitor, connected to both my Mac (USB-C) and my PC (HDMI). I've found something thing macOS Big Sur broke - the "recovery" after changing display sources.
