When a user submits a Google Form, the entry is saved as a new row in the Google Spreadsheet that is collecting the responses. The Timestamp column in the spreadsheet can help you get the Edit Response URL for any entry in the form:

// when = e.namedValues["Timestamp"].toString()

const getFormResponseURL = (when) => {
  const formUrl = SpreadsheetApp.getActive().getFormUrl();

  const form = FormApp.openByUrl(formUrl);

  const responseDate = new Date(when);

  // Gets an array of all of the form's responses after a given date and time.

  const responses = form.getResponses(responseDate);

  if (responses.length > 0) {
    return responses[0].getEditResponseUrl();
  }

  return '';
};

Also see: Get Google Forms Data in Email