I am trying to adding custom quicktags like this:

function wporg_add_quicktag_paragraph() {
    wp_add_inline_script(
        'quicktags',
        "QTags.addButton( 'title_tag', 'title', '<span class="title">', '</span>', '', '', 1);"
    );
}
add_action( 'admin_enqueue_scripts', 'wporg_add_quicktag_paragraph' );

Using <span class="title"> throws an error. But if I change <span class="title"> to <span>, it works fine.

I was able to add <span class="title"> as a quicktag until the WordPress 6.0 update. My new code is based of this: https://developer.wordpress.org/apis/quicktags/

For reference, my pre 6.0 code was as below. Obviously it doesn’t work now.

function add_quicktags() {

    if ( wp_script_is( 'quicktags' ) ) { ?>
        <script type="text/javascript">
            QTags.addButton( 'title_tag', 'title', '<span class="title">', '</span>', '', '', 1 );
        </script>
    <?php }

}
add_action( 'admin_print_footer_scripts', 'add_quicktags' );

Thanks in advance