I find it incredibly annoying that you can't control the size of the window for maple and I hate having it in full screen because I constantly tab out. I have two monitors so this solution doesn't bother me, but it probably would be if you're only using one. I leave maple on my secondary monitor and change the resolution to 1280x720 so the size of maple increases by a considerable amount. It's all the functionality size wise while still being able to play in windowed!
You could use something called "winresizer" if you're on Windows. It's been working for me pretty well c:
Is there an alternative for Mac users as well? I really want to play windowed mode, but it is just so small.
It does make it slightly blurry but it shouldn't be that bad. Alternatively, you could google a Mac substitute!