mkdocs-material/material/partials/nav-item.html

{% if nav_item.children %}
  <li class="md-nav__item md-nav__item--nested">
    {% if nav_item.active %}
      <input class="md-toggle md-nav__toggle" data-md-toggle="{{ path }}" type="checkbox" id="{{ path }}" checked>
    {% else %}
      <input class="md-toggle md-nav__toggle" data-md-toggle="{{ path }}" type="checkbox" id="{{ path }}">
    {% endif %}
    <label class="md-nav__link" for="{{ path }}">
      {{ nav_item.title }}
    </label>
    <nav class="md-nav" data-md-component="collapsible">
      <label class="md-nav__title" for="{{ path }}">
        {{ nav_item.title}}
      </label>
      <ul class="md-nav__list">
        {% for nav_item in nav_item.children %}
          {% set temp = path %}
          {% set path = path + "-" + loop.index | string %}
          {% include "partials/nav-item.html" %}
          {% set path = temp %}
        {% endfor %}
      </ul>
    </nav>
  </li>
{% elif nav_item == page %}
  <li class="md-nav__item">
    <input class="md-toggle md-nav__toggle" data-md-toggle="toc" type="checkbox" id="toc">
    <label class="md-nav__link md-nav__link--active" for="toc">
      {{ nav_item.title }}
    </label>
    <a href="{{ nav_item.url }}" title="{{ nav_item.title }}" class="md-nav__link md-nav__link--active">
      {{ nav_item.title }}
    </a>
    {% include "partials/toc.html" %}
  </li>
{% else %}
  <li class="md-nav__item">
    {% if nav_item.active %}
      <a href="{{ nav_item.url }}" title="{{ nav_item.title }}" class="md-nav__link md-nav__link--active">
        {{ nav_item.title }}
      </a>
    {% else %}
      <a href="{{ nav_item.url }}" title="{{ nav_item.title }}" class="md-nav__link">
        {{ nav_item.title }}
      </a>
    {% endif %}
  </li>
{% endif %}