ClickHouse/docs/mkdocs-material-theme/partials/nav.html

<nav class="md-nav md-nav--primary" data-md-level="0">
  <label class="md-nav__title md-nav__title--site" for="drawer">
    {{ config.site_name }}
  </label>

  <ul class="md-nav__list" data-md-scrollfix>
    <li class="md-nav__item md-nav__item--active">
      <script type="text/javascript">
        if (window.location.pathname.indexOf('/ru/') >= 0) {
          if (window.location.pathname.indexOf('/single/') >= 0){
            document.write("<a href=\"{{ base_url }}/../index.html\" class=\"md-nav__link md-nav__link--active\">Многостраничная версия документации</a>")
          }else{
            document.write("<a href=\"{{ base_url }}/single/index.html\" class=\"md-nav__link md-nav__link--active\">Одностраничная версия документации</a>")
          }
        }else{
          if (window.location.pathname.indexOf('/single/') >= 0){
            document.write("<a href=\"{{ base_url }}/../index.html\" class=\"md-nav__link md-nav__link--active\">Multi page version of the document</a>")
          }else{
            document.write("<a href=\"{{ base_url }}/single/index.html\" class=\"md-nav__link md-nav__link--active\">Single page version of the document</a>")
          }
        }
     </script>
    </li>
  </ul>

  <ul class="md-nav__list" data-md-scrollfix>
    {% for nav_item in nav %}
      {% set path = "nav-" + loop.index | string %}
      {% set level = 1 %}
      {% include "partials/nav-item.html" %}
    {% endfor %}
  </ul>
</nav>