code: public function getFieldConfiguration()
      {
          $levels = [
              '1' => '1',
              '2' => '2',
              '3' => '3',
              '4' => '4',
              '5' => '5',
              '6' => '6',
          ];
  
          $level = ($this->getSetting('Level')) ? $this->getSetting('Level') : 3;
          $label = _t('Moo_EditableFieldHeading.LEVEL', 'Select Heading Level');
  
          return [
              new DropdownField($this->getSettingName('Level'), $label, $levels, $level),
          ];
      }
docs: Get extra configuration fields.
  
  @return array