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

{% if nav_item.children or nav_item == current_page %}
  <li class="md-nav__item md-nav__item--nested">
    {% if nav_item == current_page %}
      {% set path = "toc" %}
    {% endif %}
    {% if nav_item.active and not nav_item == current_page %}
      <input class="md-toggle md-nav__toggle" type="checkbox" id="{{ path }}" checked>
    {% else %}
      <input class="md-toggle md-nav__toggle" type="checkbox" id="{{ path }}">
    {% endif %}
    {% if nav_item == current_page %}
      <label class="md-nav__link md-nav__link--active" for="{{ path }}">
        {{ 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" %}
    {% else %}
      <label class="md-nav__link" for="{{ path }}">
        {{ nav_item.title }}
      </label>
      <nav class="md-nav">
        <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>
    {% endif %}
  </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 %}