iconlist doesnt appear for me in the templates, which probably means its a php variable. So where ever that is located just needs the new icon rows added in a php if condition to add it to iconlist
$ sudo grep -ri iconlist
[sudo] password for metulburr:
inc/functions.php: $iconlist = '';
inc/functions.php: eval("\$iconlist .= \"".$templates->get("posticons_icon")."\";");
install/resources/mybb_theme.xml:<td class="trow1" valign="top">{$iconlist}</td>