This could be because when repositioning this field what gets shown is its value. But if that field doesn't yet have a value nothing is shown. You could try replacing the source code file mod/customcert/element/coursefield/classes/element.php
with the one attached to this reply. Then if the field doesn't have a value customfield_shortname is shown, for example, customfield_hours. You should then be able to drag this to the required location.