contact-form-7-thank-you-redirect.php

    add_action( 'wp_footer', 'redirect_cf7' );
     
    function redirect_cf7() {
    ?>
    <script>
    document.addEventListener( 'wpcf7mailsent', function( event ) {
           location = 'https://www.example.com/thanks/';
    }, false );
    </script>
    <?php
    }