A Drupal (8, 9) module to override the Webform Share share.js script and pass the parent page query parameters into the iframe

• copy/paste the code to embed your form using Javascript method (via the "Share" tab of the webform)
• in the pasted code replace share.js with share_params.js
• now if you display the embeding page with a query parameter like ?utm_campaign=webform_share_params_test you have it in the iframe too (and you could use it to prepopulate a field)