Add document.url as a hidden field

avada_forms_hidden_field_set_doc_url.php

<?php // Ignore this first line when copying to your child theme's functions.php file.

add_action( 'wp_footer', function () { ?>
<script>

	(function() {
		if (document.title !== "Test Form – Avada Lab") return; // Run this script on the test form page only.
		try {
			document.querySelector("#doc-url").setAttribute("value", document.URL);
		} catch (e) {
			console.log("Something wrong happened when setting the hidden doc-url value.");
		}
	})();

</script>
<?php } );
/** 
 * Add to your child theme's functions.php file, use a code snippets plugin, or your theme's custom code settings. 
 */

If you need to load your function very late on the page (i.e., after modals or popups), then change line 16 to this.

<?php }, 500 );

Increase 500 all the way up to 900 as needed. The higher the number the lower down in your page your code will load.

This isn't a guarantee since some plugins and themes are greedy and want to be the very last thing loaded (to override everything else).

If that's the case, you might need to wrap the JS in setTimeout() to delay the load even longer.