Keyboard shortcuts? This is a topic very close to my heart , as I love my keyboard. Even though my current setup uses a touchscreen, I still have a small external USB keyboard attached to the dashboard. I think everything in Garmin Mobile PC can be controlled with the keyboard, thanks to the arrow keys. But a few things could be simplified by adding a few single keystroke shortcuts.
Terry already summarised the available shortcuts. There are only few of them, and they are, for the most part, clearly marked on the screen. If there is no specific shortcut for something, most likely you can select the button, or a line, by navigating to it with ArrowUp, ArrowDown, ArrowRight, and ArrowLeft, keys.
In menus with check-boxes, you can add or remove check-marks by pressing Spacebar.