Hi @HannahSc8 ,
There is no such option out of the box. Even though once converted to project request is linked to its resolution, meaning when the project is finished the request is also marked as resolved, but I guess you already know and are not looking for this functionality.
Project resolution will always depend on the number of tasks either taken from template if you use template for creation or from tasks you manually add. But this is also just planned completion date, meaning it can be different based on any delays etc.
Best way to handle this is to have an automation build in workfront fusion to check the changes to the completion date and then update the related request planned completion date. Hopefully this makes sense.
Best regards,
Ivan