Alter the toolbar menu after hook_toolbar() is invoked.
This hook is invoked by toolbar_view() immediately after hook_toolbar(). The toolbar definitions are passed in by reference. Each element of the $items array is one item returned by a module from hook_toolbar(). Additional items may be added, or existing items altered.
$items: Associative array of toolbar menu definitions returned from hook_toolbar().
function hook_toolbar_alter(&$items) {
// Move the User tab to the right.
$items['commerce']['#weight'] = 5;
}