public function extend_navigation(global_navigation $navigation, navigation_node $node=null) {
        if (has_capability('moodle/grade:managegradingforms', $this->get_context())) {
            // No need for preview if user can manage forms, he will have link to manage.php in settings instead.
            return;
        }
        if ($this->is_form_defined() && ($options = $this->get_options()) && !empty($options['alwaysshowdefinition'])) {
            $node->add(get_string('gradingof', 'gradingform_guide', get_grading_manager($this->get_areaid())->get_area_title()),
                    new moodle_url('/grade/grading/form/'.$this->get_method_name().'/preview.php',
                        array('areaid' => $this->get_areaid())), settings_navigation::TYPE_CUSTOM);
        }
    }