Hello @vauneen,
The current version of the plugin does not include this option, because at least all required fields must be entered before submit the form, but if you tick the checkbox: “Enable the browser’s persistence” in the “Form Settings” tab the user can close the browser without submitting the form, and the next time it open the form’s page in the browser, the fields would be pre-filled in the previous values.

There is an alternative using the “Users Permissions” add-on, distributed with the Developer and Platinum versions of the plugin. The behavior wouldn’t be exactly the requested one, but activating this add-on and configuring the form to the be submitted only one time per registered user, and allowing the users edit their submissions (simply ticking a checkbox in the form’s settings), every time the user access to the form’s page, the form’s fields would be pre-filled with the values submitted previously (this time the values are not stored in the browsers, because the form was submitted previously and the values stored in the website’s database).
More information in the following links:
https://cff.dwbooster.com/add-ons/users-permissions
https://cff.dwbooster.com/documentation#users-addon
Best regards.