I believe this was raised and already shot down. However, I’d like to take another run at it…
I can tell you when I’m in the writing zone, using Full Screen, it sure would be less disruptive being able to switch out to reference the thesaurus, check a quick fact with Google, switch Internet radio stations, jot a quick email reminder to self, and then each time being able to return to Full Screen without having to invoke it again.
I realize this is non-standard. But isn’t that the whole point of Scrivener, to be a better writing tool than all the other (standard) writing tools. Perhaps this Return to Full Screen could be a mode invoked through preferences.