Topic/Subtopic Desk Theme hack. Place on Page (Index) in Advanced Theme Editor.

1 - index code

<div id="content">
  <div class="container index">
    <div class="row">
      <div class="col-md-12">
        <div class="col-md-8 {% if desk.page.theme.layout != 'left' %} col-md-push-4 {% endif %}">
          <div class="row topic">
            {% assign col = 0 %}
            {%for topic in topics%}
            {%if topic.desc contains 'heading' and col == 0 %}
          </div><div class="row topic">
          {% endif %}
          {% if topic.desc == 'heading' %}
          <h2 class="subheader col-md-12">{{ topic.name }}</h2>
          </div><div class="row topic">
          {% assign col = 0 %}
          {% else %}
          <div class="desk-topic desk-topic-{{ topic.id }} col-md-6">
            <h3><a href='{{topic.public_articles_url}}'>{{ topic.name }}</a></h3>
            <ul>
              {% for article in topic.articles limit:5 %}
              <li><a href='{{article.public_url}}'>{{ article.subject_plain }}</a></li>
              {% endfor %}
            </ul>
            <a class="btn btn-pill" href='{{topic.public_articles_url}}'><span class="desk-view-text">{{system.snippets.view_all}}</span> {{ topic.article_count }}</a>
          </div>
          {% if col == 2 %}
          </div><div class="row topic">
          {%assign col = 0 %}
          {%else%}
          {% assign col = 2 %}
          {%endif%}
          {% endif %}
          {%endfor%}
          </div>
        </div><!--Index Col 8 -->
        <!--SIDEBAR -->
        {{ sidebar_main }} <!--SIDEBAR -->
      </div><!-- Main Row-->
    </div><!--Container-->
  </div><!--Content-->