I'm using Ubuntu GNOME 16.04 with GNOME Shell 3.18.5.
I have just switched from XFCE to GNOME, and I am used to pressing Alt+Space and then C to close a window, Alt + Space and then X to maximize, etcetera. But in GNOME, I can't press those keys for those actions, because they aren't underlined:
and I have to scroll through with the arrow keys or click. Is there a way to enable those shortcuts?