Yes please. I prefer playing games in fullscreen mode, but not at the cost of knowing if I accidentally hit alt+tab (something I've done repeatedly while trying to hit my IME hotkeys) I will instantly crash the game and fail any levequests I'm on. I have multiple computers, but being able to look up things on a single computer while playing in fullscreen is kind of standard. The windowed mode also has worse performance ingame, and considering what a resource hog this game is it needs every drop it can get.

Really, this is a standard feature in any game that's been made in the past 5 years at least, I was honestly shocked when FF14 hadn't solved the problem that FFXI players have been rightfully complaining about for years.