Mac or pc? I'm on mac and I think it's shift and apostrophe ..I do it naturally without thinking but the best way to check, also for other shortcuts is to go the the little box on upper right edge of each window, here you can select the minimise or max and next to it, it will show you the keyboard shortcut.
Failing that it's rtfm.
Hope that helps.
I'm on PC.
What you suggest work for the original workspace - editing. however when I move to a workspace I have created the option to maximize is lo longer available.