code: public function getFieldConfiguration()
      {
          $groupID = ($this->getSetting('GroupID')) ? $this->getSetting('GroupID') : 0;
          $groups  = DataObject::get('Group');
  
          if ($groups) {
              $groups = $groups->map('ID', 'Title');
          }
  
          return [
              new DropdownField($this->getSettingName('GroupID'), _t('Moo_EditableField.GROUP', 'Group'), $groups, $groupID),
          ];
      }
docs: Get extra configuration fields.
  
  @return array