How to "un-maximize" or "restore" an Excel window In Excel, I have a window that uses all of the display real estate, apart from the dock area. Is there any way to make it use only part of the display, apart from resizing the window by dragging the bottom right corner of the window, or installing a third-party application?

I tried pressing the green button in the top left hand corner, and also all sensible combinations of keyboard keys plus the green button. I also examined whether the "Window" menu had anything to help do this.

"Un-maximimize" or "restore" may or may not be the correct terminology. In both Microsoft Windows, and most flavours of Linux GUIs I've encountered, you can "maximize" a window to make it use most of the display real estate, and then "restore" a window to make it shrink back to the previous size. I don't know the OS X terminology, as unlike Microsoft Windows and Linux GUIs, there isn't a menu about resizing windows. I understand that the green button in OS X isn't exactly equivalent to "maximize".
The Escape key un-maximizes Excel. Another way is to push the mouse cursor to the top edge of the screen. The menu bar would appear. A blue unmaximize button will appear in the top right corner. Finally, you can use Control Command F. That should work with all programs, not just Excel.

If you have an additional monitor and set up access to it in the "top" direction, it will not be possible to "hit" the top of the screen to get the menu bar. In this case hit the top corner of the monitor.