You want to apply, for a Sub-Task with some of their Custom Field be updated with Parent Custom Field values.
How it works
By defining this Workflow Function in a Transition of your workflow, you are able to force some of Sub-Task's Custom Field to be updated with those of Parent Issue.
Configuring the Feature
To configure the Inherit CustomFields Post-Function, please follow these steps :
Since this Workflow Function does not need to be associated with a screen containing the concerned CustomFields, the function can be added in any Workflow Transition. It might be:
A Common Transition,
Or a Global Transition.
If you want to keep these fields synchronized, it will be preferable to removed concerned CustomFields from the Edit Screen of the Sub-Task, and implement then in all transiitons.
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 :
After Create Issue Post-Function
and before index Issue Post-Function
If it is not respected you will experience an error message when trying to perform the transition.
Add the Inherit CustomFields Post-Function to any wanted transition.