Ah, interesting. FWIW, in OS X, it's "command-tab" to switch between active applications. With the "other" MMO, because it takes the whole screen over, they had to build some support. BUT for the hell of it, I gave it a shot and BINGO, it immediately dumped me out to the rest of my system where I can do what I need, then command-tab back to FFXIV (without having to mess with it's fill screen settings). And yes, going into various windowed screen modes are supported in FFXIV-Mac

Issue solved, thanks for the prod to try something I didn't think would work!