For every position in menu you have few bonus options that will be used only in Site Navigation menu:
Adding icon
If you want to add an icon to your menu item, then click on the input Item icon and you will be able to choose an icon from the set.
Making menu item not clickable
If you want the menu item to not be linked, then just mark the option Make this item normal text(will not be link) – useful for the parent of the submenu, as it will make the whole link open a submenu, instead of only small icon of the submenu opening icon.