The order that you see in the side nav are determined by the order they were added to the PowerCMS. There are no options for reordering the contents in this area. This portion of the page is controlled with the code on the pages.php page in the admin area. In here the recordsets are defined that make the listings, it is possible that you could alter the recordsets here to come up with a different listing. This type of custom editing is not supported though so if you attempt it you should make a backup of any pages first in case you need to revert to them.