magento-test/app/code/Magento/Ui/view/base/web/templates/tab.html

<!--
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
-->
<div class="admin__page-nav">
    <div class="admin__page-nav-title" css="_collapsible: collapsible, _opened: opened && collapsible" click="toggleOpened" keyboard="13: toggleOpened">
        <strong tabindex="1" text="label" keyboard="13: toggleOpened"></strong>
    </div>
    <ul class="admin__page-nav-items items" each="elems" visible="opened">
        <li class="admin__page-nav-item" tabindex="2" css="_active: active, _loading: loading" click="activate" keyboard="13: activate">
            <a class="admin__page-nav-link" href="#" css="_changed: changed" attr="id: 'tab_' + index">
                <span text="label"></span>
                <span class="admin__page-nav-item-messages">
                    <span class="admin__page-nav-item-message _changed">
                        <span class="admin__page-nav-item-message-icon"></span>
                        <span class="admin__page-nav-item-message-tooltip"
                               translate="'Changes have been made to this section that have not been saved.'"></span>
                    </span>
                    <span class="admin__page-nav-item-message-loader">
                        <span class="spinner">
                           <span repeat="8"></span>
                        </span>
                   </span>
                </span>
            </a>
        </li>
    </ul>
</div>