That...might be the problem! There doesn't seem to be any such window. All the UI I see on a Mac, or at least on this Mac, is this: 
(The other Mac to which I have access is my work machine, which...no. But this is OS X 10.9.something or other, and I don't think 10.12 is likely to be all that different! And it is possible the window's just rendering offscreen; Godot seems to be doing some weird things with window placement overall, which might be because it doesn't know how to handle high-DPI displays well, I'm not sure. Exposé isn't showing me but the one window for Fursona Creator, though, so I'm pretty sure it's just not there...)