grafana/panels/fields/module.html

<div ng-controller='fields'>
  <h4 ng-class="{'ng-cloak': !panel.title}">{{panel.title}}</h4>
  <ul class="nav nav-list" style="height:{{row.height}};overflow-y:auto;overflow-x:hidden;">
    <li ng-style="panel.style" ng-repeat="field in fields" ng-class="is_active(field)" ng-click="toggle_field(field)"><a>{{field}}</a></li>
  </ul>
</div>