wms-menu/assets/css/_wms_extend_menu.css

@media (max-width: 768px) {
    .layout-cell.layout-sidenav-container.wms-menu {
        display: none;
    }
    .sidenav-tree-root .sidenav-tree .back-link.wms-menu-back-link {
        display: block !important;
    }
    .layout-cell.layout-sidenav-container ~ .layout-cell.sidenav-tree {
        border: none;
    }
}