If you are adding items to the collection on the T1, then you would have to delete the existing collection and then recreate it and add the book you want as the new #1 first. Not really an efficient or workable solution for long lists. It is is one of my biggest frustrations with the new Sony software that you can't manually drag-and-drop items in the collection list anymore.
Maybe there is a way to do it with calibre? I don't use calibre with my Sony ereaders so I'm not sure.