Webflow Forms + Redirect with URL Parameters

I am trying to submit a simple waitlist form that includes the following fields:

  1. Email address
  2. Referral code
  3. Referred BY code

Both 2 and 3 are hidden fields. 2 is auto generated using basic Javascript while 3 is pulled out of the url.

The desired behavior on form submission is that the users auto-generated referral code is forwarded to a redirect URL for a “success” page. That page should then include that user’s unique referral link that they can share and forward to friends.

The issue arises when I try to redirect the user after submitting the form. If I set the redirect URL for the form to the success page, the user’s submission is saved, but I have no way of adding the user’s referral code as a URL parameter. If I set the form submission button to Action: URL as a POST method… I now get the desired URL, but my form is no longer saved in the Webflow backend. I need both the URL parameter sent to the redirect AND the form submission to save to the Webflow backend.

Please help! This is extremely frustrating for such a simple scenario.

Here is my site Read-Only: LINK
(how to share your site Read-Only link)