Edit form after submit

After clicking on submit, you cannot edit a form. You will need to set-up a related action to make changes to what is already saved. 

docs.appian.com/.../record-actions.html

Can you explain your use case in more detail?

Conceptually there's not even really such a thing as "edit a form after submit" - i think you need to back it up a bit and describe more plainly what user experience you're hoping to provide.