I still don't fully understand how to gracefully have multiple desktop environments and switch between them. When I want to try something new to me like lxqt, I usually spin up a VM.
find a dropdown or cogwheel where you can select the other desktop environment
log in
Having said that, I don't know what you mean with "graceful". Desktop environments may involve lots of packages, which may create configuration files in your home directory or get auto-started in your other DEs, so it can be messy.
Something minimal, like LXQt or the various window managers, isn't going to cause much of a mess, though.
I guess, creating a second user with a separate home-directory, like the other person suggested, would isolate that potential mess...
Create a different user for each desktop environment.
Put all the users in a group that has full write access to a shared folder you use for your files.