Can you arrange the order of tasks in the Today screen after assign them a priority?
unfortunately, it's not possible to manually reorder tasks on the Today search result page. You can use priorities or due times (tod at 16:30 will be above tod at 16:31) to influence the order, though.
Still, we may consider adding such feature in the future. You're welcome to vote for this request in our Votebox: http://todoist.com/Vote/showProposal/64/