What is Priority Mail? Priority Mail is First-Class Mail that weighs over 13 ounces. All matter that is mailable by air can be mailed as Priority Mail.
The USPS does support Priority mail. You can find more information here: http://pe.usps.com/text/dmm300/dmm300_landing.htm.
Currently Presort and Label Studio do not support Priority Mail.
However, there is an enhancement that has been written up for Presort to support this. Once Presort supports Priority Mail, Label Studio would pick this enhancement up as well. If you would like to be added to the enhancement, please log a message for Customer Support and refer to KB article 1192227