openproject/frontend/public/templates/components/toggled_multiselect.html

<div>
  <select filter-value-select
          ng-if="!isMultiselect"
          name="v[{{name}}][]"
          ng-model="$parent.values"
          ng-disabled="disabled"
          id="values-{{name}}"
          class="select-small"
          style="vertical-align: top;"
          require>
    <option ng-repeat="value in availableOptions" value="{{ value[1] }}" ng-selected="isSelected(value[1])" label="{{ value[0] }}">{{ value[0] }}</option>
  </select>

  <select multiple
          filter-value-select
          ng-if="isMultiselect"
          name="v[{{name}}][]"
          ng-model="$parent.values"
          ng-disabled="disabled"
          id="values-{{name}}"
          class="select-small"
          style="vertical-align: top;"
          require>
    <option ng-repeat="value in availableOptions" value="{{ value[1] }}" ng-selected="isSelected(value[1])" label="{{ value[0] }}">{{ value[0] }}</option>
  </select>

  <a href class="no-decoration-on-hover" title="{{I18n.t('js.work_packages.label_enable_multi_select')}}" ng-click="toggleMultiselect()">
    <icon-wrapper icon-name="plus"
                  icon-title="{{I18n.t('js.work_packages.label_enable_multi_select')}}"/>
  </a>
</div>