Add a callback to inject nodes in the category settings navigation

1. Add something like this to a plugin, in this case mod_chat:

   function chat_extend_navigation_category_settings(navigation_node $node, context $context) {

   $node->add('test', new moodle_url('/test', array('ctx' => $context->id)), navigation_node::TYPE_SETTING, null, null, new pix_icon('i/edit', ''));

   }

2. Confirm that a new link 'Test' is displayed in the administration block for a category.
   • E.g. at course/index.php?categoryid=1

You might need to purge your caches.