discourse/app/assets/javascripts/admin/templates/modal/site-customization-change.hbs

<div>
  <ul class="nav nav-pills">
    <li class="{{if newSelected 'active'}}">
      <a href {{action "selectNew"}}>{{i18n 'admin.logs.staff_actions.new_value'}}</a>
    </li>
    <li class="{{if previousSelected 'active'}}">
      <a href {{action "selectPrevious"}}>{{i18n 'admin.logs.staff_actions.previous_value'}}</a>
    </li>
  </ul>
  {{#d-modal-body title="admin.logs.staff_actions.modal_title"}}
    <div class="modal-tab new-tab {{unless newSelected 'invisible'}}">
      {{#if model.new_value}}
        {{site-customization-change-details change=model.new_value}}
      {{else}}
        {{i18n 'admin.logs.staff_actions.deleted'}}
      {{/if}}
    </div>
    <div class="modal-tab previous-tab {{unless previousSelected 'invisible'}}">
      {{#if model.previous_value}}
        {{site-customization-change-details change=model.previous_value}}
      {{else}}
        {{i18n 'admin.logs.staff_actions.no_previous'}}
      {{/if}}
    </div>
  {{/d-modal-body}}
  <div class="modal-footer">
    <button class='btn btn-primary' {{action "closeModal"}}>{{i18n 'close'}}</button>
  </div>
</div>