Going to the Advanced tab of Form Workflow Plus will give you some more options.
1/ Responses settings
=> In order to enable "Send back to requestor" functionality, complete first 3/, then tick "Allow Send back to requestor"
=> Tick "Allow on Hold" to authorize reviewers to put requests on hold
2/ Validation auto reminder
Click on "Activate reminder" for reviewers to be reminded by email once a day of all their pending "Waiting for validation" requests.
3/ Requestor email
Select the Sheet column containing the requestor(s) email address, in order to enable "Send back to requestor" functionality in response settings 1/
4/ Final notification
Enter the email address of the person(s) you want to be notified in cc of the final notification to the requestor.
5/ Email template
Click on + to personalize your email template.
Choose from the available fields list to personalize your template.