To add a new group subpage example group/id/abc you need to add a hook. https://github.com/opensource-socialnetwork/GroupModerators/blob/main/ossn_com.php#L15
~~~
<?php
function my_component_init(){
ossn_add_hook('group', 'subpage', 'my_component_hook');
}
function my_component_hook($hook, $type, $return = null, $params){
if($params['subpage'] == 'abc'){
return 'my page goes here';
}
}
ossn_register_callback('ossn', 'init', 'my_component_init');
~~~

Group subpage add