As far as I can tell, there is no permission for form-approval. It would be useful if users could be given the permission to only approve or deny a form-submission, rather than being assigned as administrators.
There is an approval workflow feature in the most recent release (v 11). Is that what you need? http://help.machform.com/m/using-machform/l/763652-approval-workflow-overview
Yes, but it is only available for users with the role Administrator. There is no permission which grants the Approval-role for the form: https://i.snipboard.io/NA7Trz.jpg