the only way I have found to do it is to add the tickets in reverse order, the first one is the lowest on the list, the last ticket entered is the top of the list. I wish there was an easy way to drag and drop to sort them in any order!
For reference, there is a workaround. You just need to change the 'post date' for each one. It sorts by that. But yes, it would be REALLY NICE to have the tickets allow a sorting order in them.
Via https://wordpress.org/support/topic/sorting-tickets/: