code: public function addTemplateWarning()
  	{
  		if (Contao\Input::get('act') && Contao\Input::get('act') != 'select')
  		{
  			return;
  		}
  
  		$objResult = $this->Database->query("SELECT COUNT(*) AS cnt FROM tl_user_group WHERE modules LIKE '%\"tpl_editor\"%'");
  
  		if ($objResult->cnt > 0)
  		{
  			Contao\Message::addInfo($GLOBALS['TL_LANG']['MSC']['groupTemplateEditor']);
  		}
  	}
docs: Add a warning if there are users with access to the template editor.