If you are wondering how to recover from a situation when you are locked in the lock screen, without rebooting and potentially loosing your work, a quick trick:
Press Alt+Ctrl+F2 and login as user
init 3
init 5
Login
Alt+Ctrl+F2 and logout from console session
Alt+F1 to go back to X
All your running VMs and open windows should be the same as before locking the screen.
hidden: In which I question this genius solution...
Is it sure that runlevel 3 does not close the xserver?
There is a different work-around to kill screensaver processes. It seems somehow safer…
After that, it is (maybe) necessary to restart screensaver, but it will be better to install the testing version from that thread, to avoid being again locked out.
After thinking, it seems obvious that the displays of the VMs should be able to survive. How completely brilliant!
I must learn more about the mechanism of it, to get even more free of unhealthy bare-metal thinking. Now I just want to get to a qubes machine and play.
It is just another wonderful reason to love Qubes-os!