I use email-ext plugin to be able to manage notifications for many different jobs. I would like to be able to change email priority for important jobs, less priority for something simple like a failed unit test, so forth using the email-ext from within a pipeline.

According to this stackoverflow this currently isn't possible but is easily implementable: https://stackoverflow.com/questions/7497955/jenkins-ci-how-to-add-importance-property-to-email-header