In Shopware 6.4 the service menu dropdown in topbar has been removed and moved to footer for mobile view only. If you want to re-include the dropdown just use the following steps.
include following file in your theme: \views\storefront\layout\header\actions\service-menu-widget.html.twig
{% sw_include '@Storefront/storefront/layout/header/actions/service-menu-widget.html.twig' %} Example for include: \views\storefront\layout\header\header.html.twig
Paste code from example.scss
Depending on your environment