Request form - Reschedule Copied tasks from a custom field

Hi!  

I have a request form we use for blog posts.  I had it set to pick up a template and reschedule the tasks based on the project end date which was also the publish date.  However the user has requested an additional task to promote on social media AFTER the Publish date.  It's not a huge concern about when the social promotion happens but the publish date is and the tasks should anchor to that date.

I created a custom field thinking The only option that I can see is to break the finish to start dependency and make them concurrent tasks.