<nav class=“side-pane”>

<ul class="side-pane__menu">
  {% assign collections = site.collections | sort: 'order' %}
  {% for collection in collections %}
      {% if collection.docs %}
      <li class="side-pane__title"><h3>{{ collection.title }}</h3></li>
      {% for col_page in collection.docs %}
      <li {% if page.id == col_page.id %}class="active"{% endif %}>
          <a class="side-pane__link" href="{{ col_page.url | relative_url }}">{{ col_page.label| default: col_page.title | escape }}</a>
      </li>
      {% endfor %}
      {% endif %}
  {% endfor %}
</ul>

</nav>