code: public function enableTemplateHintsAction()
      {
          try {
              $this->getService()->setTemplateHints(1);
              $this->getService()->flushCache();
              // no need to notify customer - it's obvious if they were enabled
  
          } catch (Exception $e) {
              $message = $this->__('Template hints cannot be enabled: %s', $e->getMessage());
              $this->getSession()->addError($message);
          }
  
          $this->_redirectReferer();
      }
docs: Enables template Hints