A separator creates a visual break in the navigation, like so:


A new separator can be created like so:
  • Click New... below the left side links.
  • In the pop-up window, click the More... link.
  • Check the Separator option.
  • Click Save.

The new separator can be drug into place on the navigation.  The separator color can also be set to the same background color as the site so it that becomes invisible, but still provides additional space.  Set the color in the section separators color setting in the Look and Feel tab.