script.liquid

{% if event.preview %}
  {% assign order = '{"admin_graphql_api_id":"gid://shopify/Order/1234567890"}' | parse_json %}
  {% assign order["email"] = "customer@example.com" %}
  {% assign order["tags"] = options.email_trigger_tag__required %}
{% endif %}

{% assign email_recipient = order.email %}
{% assign email_trigger_root = options.email_trigger_tag__required %}
{% assign email_trigger_root_to_match = email_trigger_root | downcase %}
{% assign email_sent_root = options.email_sent_tag__required %}
{% assign email_sent_root_to_match = email_sent_root | downcase %}

{% assign email_recipients = array %}
{% assign order_tags_to_add = array %}
{% assign order_tags_to_remove = array %}

{% assign order_tags = order.tags | downcase | split: ", " %}

{% for order_tag in order_tags %}
  {% assign new_email_recipient = nil %}

  {% assign parts = order_tag | downcase | split: ":" %}
  {% if parts[0] == email_trigger_root_to_match %}
    {% if parts.size == 1 %}
      {% assign new_email_recipient = order.email %}
    {% elsif parts[1] contains "@" %}
      {% assign new_email_recipient = parts[1] %}
    {% endif %}
  {% endif %}

  {% if new_email_recipient != blank %}
    {% assign email_recipients[email_recipients.size] = new_email_recipient %}
    {% assign order_tags_to_remove[order_tags_to_remove.size] = order_tag %}
    {% assign order_tags_to_add[order_tags_to_add.size] = email_sent_root | append: ":" | append: new_email_recipient %}
  {% endif %}
{% endfor %}

{% for email_recipient in email_recipients %}
  {% action "email" %}
    {
      "to": {{ email_recipient | json }},
      "subject": {{ options.email_subject__required | json }},
      "body": {{ options.email_body_html__required_multiline_code | strip | json }},
      "reply_to": {{ shop.customer_email | json }},
      "from_display_name": {{ shop.name | json }}
    }
  {% endaction %}
{% endfor %}

{% if order_tags_to_add != blank or order_tags_to_remove != blank %}
  {% action "shopify" %}
    mutation {
      {% if order_tags_to_add != blank %}
        tagsAdd(
          id: {{ order.admin_graphql_api_id | json }}
          tags: {{ order_tags_to_add | json }}
        ) {
          userErrors {
            field
            message
          }
        }
      {% endif %}

      {% if order_tags_to_remove != blank %}
        tagsRemove(
          id: {{ order.admin_graphql_api_id | json }}
          tags: {{ order_tags_to_remove | json }}
        ) {
          userErrors {
            field
            message
          }
        }
      {% endif %}
    }
  {% endaction %}
{% endif %}