openproject/public/templates/work_packages/modals/group_by.html

<div class="ng-modal-window">
  <div class="ng-modal-inner">
    <a href class="ng-modal-close" ng-click="modal.closeMe()">&nbsp;</a>

    <h1>Group by</h1>

    <div>
      <input id="selected_columns_new"
             type="hidden"
             ui-select2-sortable="select2Options"
             simple-query="getGroupableColumnsData"
             ng-model="selectedGroupByData"></input>
    </div>
    <div>
      <button ng-click="updateGroupBy()">Apply</button>
      <button ng-click="modal.closeMe()">Cancel</button>
    </div>

  </div>
</div>