allow users to continue the survey (webform) if closed by accident
It's simple. Go to your webform and add page break type wherever you want to split the form.

Then go to Form Settings and check Automatically save as draft between pages and when there are validation errors. or Show &quot;Save draft&quot; button.

If you want to go further, meaning if you want to save a draft when user closes the browser. check Use AJAX to auto save a draft