Hi
First of all... amazing plugin. Such an extensive array of features - it's an incredibly powerful and become increasingly valuable.
A really simple feature that would be very useful would be a button/link beneath each form when viewing your list of forms, which allowed you to send a test submission through the form to check if it was working with a single click.
This would save the arduous task of filling out the form every time... The test would obviously ignore 'no duplicate' rules but apart from that at least it would check whether the form was working otherwise. Testing a no duplicate form is a nightmare as well especially if it's integrated with the user registration plugin as you will likely run out of email addresses you can test it with and have to go and delete the user and the email address from the form entries before testing again. Perhaps a button for removing a new user and entry might be helpful as well?
It needs a little more thought obviously, but you get the idea.
Thanks!