Incluir en la plantilla /woocommerce/emails/customer-completed-order.php el seguimiento de la agencia de envio

Buenas tardes.

Para los emails que enviamos a los clientes cuando un pedido esta completado estamos usando "/woocommerce/emails/customer-completed-order.php".

Esta todo correcto pero nos gustaría incorporar el numero de seguimiento de la agencia de transporte.

Es decir, cuando cambiemos de estado el pedido a COMPLETADO introduciremos el numero de seguimiento y nos gustaría que se enviase en el correo.

Entiendo que no debe ser complicado pero si me pueden indicar el código y la variable que debería usar para incorporarlo os lo agradecería.

Código actual:

<?php
/**
* Customer completed order email
*
* This template can be overridden by copying it to yourtheme/woocommerce/emails/customer-completed-order.php.
*
* HOWEVER, on occasion WooCommerce will need to update template files and you
* (the theme developer) will need to copy the new files to your theme to
* maintain compatibility. We try to do this as little as possible, but it does
* happen. When this occurs the version of the template file will be bumped and
* the readme will list any important changes.
*
* @see https://docs.woocommerce.com/document/template-structure/
* @package WooCommerce\Templates\Emails
* @version 3.7.0
*/

if (!defined('ABSPATH')) {
exit;
}

/*
* @hooked WC_Emails::email_header() Output the email header
*/
do_action('woocommerce_email_header', $email_heading, $email); ?>

<?php
/* translators: %s: Customer first name */ ?>
<p><?php
printf(esc_html__('Hola %s,', 'woocommerce'), esc_html($order->get_billing_first_name())); ?></p>
<p><?php
esc_html_e('hemos enviado tu pedido, en 24-48h lo tendrás contigo', 'woocommerce'); ?></p>
<?php

/*
* @hooked WC_Emails::order_details() Shows the order details table.
* @hooked WC_Structured_Data::generate_order_data() Generates structured data.
* @hooked WC_Structured_Data::output_structured_data() Outputs structured data.
* @since 2.5.0
*/
do_action('woocommerce_email_order_details', $order, $sent_to_admin, $plain_text, $email);

/*
* @hooked WC_Emails::order_meta() Shows order meta data.
*/
do_action('woocommerce_email_order_meta', $order, $sent_to_admin, $plain_text, $email);

/*
* @hooked WC_Emails::customer_details() Shows customer details
* @hooked WC_Emails::email_address() Shows email address
*/
do_action('woocommerce_email_customer_details', $order, $sent_to_admin, $plain_text, $email);

/**
* Show user-defined additional content - this is set in each email's settings.
*/
if ($additional_content) {
echo wp_kses_post(wpautop(wptexturize($additional_content)));
}

/*
* @hooked WC_Emails::email_footer() Output the email footer
*/
do_action('woocommerce_email_footer', $email);

Muchas gracias

saludos

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