it does nothing from what I can see and it even looks like a bug.
the function for "construct_nav_option" looks like
Code:
function construct_nav_option($title, $url, $extra = '')
though, $extra is never used in within it... however $_extra is used, which is naturally empty all the time. I tried changing that to $extra but that just puts vertical bars after the the options with it. Looks like they were trying to do something by separating some options by vertical bars but then stopped halfway through. Maybe due for a later release?
but doesn't do anything atm