<div class="docs-nav-mobile unit whole show-on-mobiles">
  <select onchange="if (this.value) window.location.href=this.value">
    <option value="">Navigate the docs…</option>
    {% for section in site.data.docs_nav -%}
    <optgroup label="{{ section.title }}">
    {%- for item in section.docs -%}
      {% assign p = site.docs | where: "url", item.link | first %}
      <option value="{{ p.url | relative_url }}">
        {{- p.menu_name | default: p.title -}}
      </option>
    {%- endfor %}
    </optgroup>
    {% endfor -%}
  </select>
</div>
