system-admin-index.html.twig

{#
/**
 * @file
 * Theme override for the admin index page.
 *
 * Available variables:
 * - system_compact_link: Themed link to toggle compact view.
 * - containers: A list of administrative containers keyed by position: left or
 *   right. Each container in the list contains:
 *   - blocks: A list of administrative blocks, rendered
 *     through admin-block.html.twig.
 *
 * @see template_preprocess_system_admin_index()
 */
#}
<div class="admin clearfix">
  {{ system_compact_link }}
  {% for position, blocks in containers %}
    <div class="{{ position }} clearfix">
      {% for block in blocks %}
        {{ block }}
      {% endfor %}
    </div>
  {% endfor %}
</div>