NOTE: In this example you will see how to add keyboard shortcuts for submenus in a menu bar.
Shift + 1: First element (Communication)
Shift + 2: Second element (Shopping)
Shift + 3: Third element (Entertainment)
Shift + 4: Fourth element (Information)
Click here to select the Third element
Ctrl + Alt + P: Select the PIM submenu inside the First element (Communication -> PIM)