Actually, this is pretty easy, just do something like this in your theme file:
function nav_list($navigation, $class, $level=null)
{
$this->output('<UL CLASS="qa-'.$class.'-list'.(isset($level) ? (' qa-'.$class.'-list-'.$level) : '').'">');
if($class=='nav-main') {
$new_order = array('custom-1','ask','tag','unanswered','questions','user','admin','custom-6','custom-5');
$temp_nav = array();
foreach ($new_order as $key) {
if(isset($navigation[$key]))
$temp_nav[$key] = $navigation[$key];
}
$navigation = $temp_nav;
}
$index=0;
foreach ($navigation as $key => $navlink) {
$this->set_context('nav_key', $key);
$this->set_context('nav_index', $index++);
$this->nav_item($key, $navlink, $class, $level);
}
$this->clear_context('nav_key');
$this->clear_context('nav_index');
$this->output('</UL>');
}
Where $new_order is an array of the items you want in the order you want them - do print_r($navigation) to see what keys are for what items.