{%- set categories = resource.pages|get_all_category %}
{%- set items = resource.pages|find_category(post.meta.category) %}
<aside class="aside-container">
  <ul>
  {%- for category in categories %}
    <li>
      <h4>{{category}}</h4>
      <ul>
        {%- for item in items %}
        <li class="{%- if item.title === post.title %}current{%- endif %}">
          <a href="{{permalink_url(item)}}">{{item.title}}</a>
        </li>
        {%- endfor %}
      </ul>
    </li>
  {%- endfor %}
  </ul>
</aside>