As title says. Obviously I could setup different virtual machines or spend the time and install all the DEs in one VM if it is even possible without breaking the OS. I'm wondering if there is an already made iso or something that installs all the maintained DEs for trying.
Well, you can roll back with a switch too; no reboot required.
The VM protects you from accidental state modification however (i.e. programs enabled by some DE by default writing their config files everwhere) and its ephemeral nature makes a few things easier.
I've had some changes where I had to logout after a switch, so this should help sometimes.