coderedcms/wagtailcrx/templates/wagtailadmin/block_forms/base_block_settings_struct.html

{% load wagtailadmin_tags  %}

<div class="{{ classname }} codered-collapsible collapsed c-sf-container">
  <button type="button" class="button button-small">
    <i class="icon icon-fa-cog" aria-hidden="true"></i> Advanced Settings
  </button>
  <div class="codered-collapsible-target" style="display:none;">
    {% for child in children.values %}
    <div class="field {% if child.block.required %}required{% endif %}" data-contentpath="{{ child.block.name }}">
      {% if child.block.label %}
      <label class="field__label" {% if child.id_for_label %}for="{{ child.id_for_label }}"{% endif %}>{{ child.block.label }}</label>
      {% endif %}
      {{ child.render_form }}
    </div>
    {% endfor %}
  </div>
</div>