Redirect the vendor to a custom script so you can ask for more information about its profile or the listing.

add_redirect_url_to_listing_form.js

// Add a redirect_url to the form to create an extra step
let redirectUrlInput = document.createElement("input");
redirectUrlInput.setAttribute('name', 'redirect_url');
redirectUrlInput.setAttribute('value', 'https://your-script-url.com');
redirectUrlInput.setAttribute('type', 'hidden');

document.getElementById('listingForm').appendChild(redirectUrlInput);