I asked this question in Altassian Answers, but it seems like there is no possible way to do this now, the question is in (https://answers.atlassian.com/questions/154529/is-there-a-way-to-set-field-value-from-parent-but-not-replacing-the-existing-value)

Is there a way to Set Field Value from Parent but not replacing the existing value?

Basically, I am looking for a way to set a value from parent's issue only if the person who file the subtask didn't put a value for a specific field.

Currently, the Set Field Value from Parent is limited to replace existing values which is limited for us.

The example I used is component.

For example, I have a workflow to set component from a parent task. However, we would like the ability for users to put in the necessary component even if it's a different component from the parent's task.

Parent Task has component "A"

I created a subtask under that Parent Task, but fills in component "B"

Ends result right now is that my Subtask has component "A" and component "B" was removed.

Thanks in advance.