You want to apply, for a Sub-Task, the same Priority as its Parent Issue.
By defining this Workflow Function in a Transition of your workflow, you are able to force Sub-Task's Priority to be updated with Priority of Parent Issue.
To configure the Inherit Priority Post-Function, please follow these steps :
Note that if you need to use such Post-Function in a Initial Transition (Create Transition), you have to check that the Post-Function is used :
If it is not respected you will experience an error message when trying to perform the transition.
And the XML Declaration as follow :
On this page:
See also ...