wagtail/wagtail/admin/templates/wagtailadmin/block_forms/stream.html

{% extends "wagtailadmin/block_forms/sequence.html" %}

{% block header %}
    {% if list_members_html %}
        {% include "wagtailadmin/block_forms/stream_menu.html" with menu_id=prefix|add:"-prependmenu" state="closed" %}
    {% else %}
        {% include "wagtailadmin/block_forms/stream_menu.html" with menu_id=prefix|add:"-prependmenu" state="open" %}
    {% endif %}
{% endblock %}