After the user fills out the form, you may want to provide two different buttons: one to save the form so they can return later, and one to finalize the form submission. On the two buttons below, go to Properties > Events and review the event mappings. On the Save button you will see the Form: Save event along with an Email: Send event. The email uses the @@SubmissionID value to create a URL that can be used to reactivate the form. This URL will need to be added in by the form manager and point to the main view of the form and add &submission_id=@@SubmissionID to the URL query string. Alternatively, an authenticated user will be prompted to pick up where they left off when accessing the form.