Administrators will now have the ability to toggle the send back and denial options in a workflow. This will allow App Admins to specify the stages at which approvers can or cannot send back or deny form submissions, or turn off/on the options for the entire workflow. 

For task steps, Administrators can only enable or disable send-back in task steps.

*Note that this feature will not apply retroactively to documents that are already in the workflow.

Read more about this feature HERE