There is no field in manage display of content type to display Flag link.
There is a tpl file (**node--article--teaser.tpl.php**) for teaser mode displaying bookmark

    <?php if (isset($content['links']['flag'])) : ?>
        <?php echo render($content['links']['flag']);?>
    <?php endif; ?>

But for another mode this having View mode *teaser_2_col* and tpl file name **node--teaser-2-col.tpl.php**, `$content['links']` does not have a Flag element.