Ideally on Sub-Task Create I would like to display the parent Summary field as the default Summary and allow the user to edit that. I found deferred feature requests so this appears not to be possible.
As an alternative, not displaying the Summary field and having the parent Summary copied into the Sub-Task summary on create would be acceptable. Users could then edit the Sub-Task if they wanted to change the Summary.
I tried implementing the above by not showing the Summary field on the create screen and adding a post function to copy the parent's Summary field into the Sub-Task Summary field. But creates then fail because the Summary field not empty validation precedes the post function.
Is there a way to copy the field value earlier OR to, without user interaction, add a dummy value to the Summary field to pass the validation check (and be overwritten by the post function)?