silverstripe-cms/templates/SilverStripe/CMS/Controllers/Includes/CMSMain_ViewControls.ss

<div class="view-controls view-controls--{$ViewState}">
    <%-- Change to data-pjax-target="Content-PageList" to enable in-edit listview --%>
    <a class="page-view-link btn btn-secondary btn--icon-sm btn--no-text font-icon-tree"
        href="$LinkTreeView.ATT"
        data-view="treeview"
        data-pjax-target="$PJAXTarget.ATT"
        title="<% _t('SilverStripe\CMS\Controllers\CMSPagesController.TreeView', 'Tree View') %>"
    ></a>
    <a class="page-view-link btn btn-secondary btn--icon-sm btn--no-text font-icon-list"
        href="$LinkListView.ATT"
        data-view="listview"
        data-pjax-target="$PJAXTarget.ATT"
        title="<% _t('SilverStripe\CMS\Controllers\CMSPagesController.ListView', 'List View') %>"
    ></a>
</div>