How to add a new button on post

in the free theme Customizr, you can add content after the edit link with this code in the file functions.php of the child theme

add_action("__after_regular_heading_title", function () {

    $post = $GLOBALS["post"];

    ?>

        <span>
            an addition after the link to edit
            "<?php echo htmlspecialchars($post->post_title);?>"
        </span>

    <?php

});