I have a laptop running Qubes and SOMETIMES it would be nice to use it as an extra screen in my synergy setup when I'm doing dev work. I could just duel boot it for said purpose, but that's annoying.

I got Synergy running in a Debian appVM and made some port forwarding rules which got the Synergy client to actually connect. Then I messed around with USB services with no success. The mouse just disappears when it should jump over to the Qubes machine.

Anyone out there who's made this work or who has a good understanding of what it might take?

Yes, I DO realize using Qubes in this way is circumventing part of the whole point of having Qubes in the first place.