This didn't seem to be working for me, but from another post by a JotFo

This didn't seem to be working for me, but from another post by a JotForm staff member it appears this method of assigning a session ID only works BEFORE the user submits the form. Key phrase from that response:

QUOTE - "This is not the edit link - the session is active only until the form is submitted, so as soon as they make a submission, they can not longer use it."

So it's a way the responder can continue working on a long form BEFORE they submit it, but not a method to edit a submitted form. Once the form is submitted, they'll no longer be able to access it at the ?session=whatever URL.

That was the missing piece for me and I thought I'd clarify given the number of people who, like me, found that this didn't work as I expected it to (before and after submission). Hope this clarification helps. The reply that I referenced above is found in this thread:

https://www.jotform.com/answers/650286-Edit-link-is-not-working-for-our-customers

That is correct statement. Save form and Continue Later feature helps user to save the progress of form so that they can submit it later. Once a form is submitted, the saved input data in session is cleared.. If you access the same URL again, it will not display the saved input data.

Save form and Continue Later feature will not work to edit submissions. If you need to edit any submissions, it can only be edited by using form's edit URL.