nav.html

{% if not nav_item.children %}
<li {% if nav_item.active %}class="elem-active{% if page.toc %} elem-toc{% endif %}" {% endif %}>
    {% if nav_item.active %}
    <a href="{{ (page.toc|first).url }}" class="elem-text">{{ nav_item.title }}</a>
    {% else %}
    <a href="{{ nav_item.url }}" class="elem-text">{{ nav_item.title }}</a>
    {% endif %}
    {% if nav_item.active %}
    <ul class="table-of-contents">
        {% for toc_item in page.toc %}
        {% if toc_item != (page.toc|first) %}
        <li class="toc-item"><a href="{{ toc_item.url }}">{{ toc_item.title }}</a></li>
        {% endif %}
        {% for toc_item in toc_item.children %}
        <li class="toc-subitem"><a href="{{ toc_item.url }}">{{ toc_item.title }}</a></li>
        {% endfor %}
        {% endfor %}
    </ul>
    {% endif %}
</li>
{% else %}
<li class="elem-parent">
    {% if nav_item.children.active %}
    <a href="{{ (page.toc|first).url }}" class="elem-text">{{ nav_item.title }}</a>
    {% else %}
    <a href="#" class="elem-text toggle-collapsible"><span class="fa fa-plus collapsible-icon"></span> {{ nav_item.title }}</a>
    {% endif %}
    <ul class="nav-collapsible {% if nav_item.active %}nav-collapsible-open{% endif %}">
        {% for nav_item in nav_item.children %}
        {% include "nav.html" %}
        {% endfor %}
    </ul>
</li>
{% endif %}