I'm not sure if this is what you're looking for, but the first thing I enable on a new install is tabbing between UI elements and pressing enter to use them. I

I'm not sure if this is what you're looking for, but the first thing I enable on a new install is tabbing between UI elements and pressing enter to use them. If you go into System Preferences -> Keyboard -> Shortcuts (tab) There will be a checkbox at the bottom that says 'use keyboard navigation to move focus between controls'. This will do what it says! Hope this helps.