-----------------------------
ADD this to Contact Form 7
-----------------------------

[text page-url]

-----------------------------
ADD this to Mail on Contact Form 7
-----------------------------

Page URL
[page-url] 

-----------------------------
ADD this to functions.php
-----------------------------

function customize_contact_form() {
    ?>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
    <script>
document.addEventListener('DOMContentLoaded', function() {
    // Get the page URL
    var pageUrl = window.location.href;

    // Set the value of the "page-url" input
    var urlField = document.querySelector('[name="page-url"]');
    if (urlField) {
        urlField.value = pageUrl;
    }
});
</script>
    <?php
}
add_action('wp_footer', 'customize_contact_form');

--------------------------------------------------
CSS
--------------------------------------------------

 .wpcf7-form-control-wrap[data-name=page-url] {
    display: none;
} 