Priority is included in the "Status" Visible Field. This includes four icons which represent the ticket status, follow up, priority, and pin status. When viewing tickets in the content preview pane you can sort the tickets by clicking on Status. This will list the tickets in order based on the four Status options.
You may also configure your own Custom Field for priority. Custom fields can be chosen in the Visible Fields section to include in the content preview pane toolbar.
I hope this helps!