Template to attach shipment tracking number in WooCommerce Email Customizer with Drag and Drop Email Builder. WooCommerce Shipment Tracking Pro - https://www.pluginhive.com/product/woocommerce-shipment-tracking-pro/

custom_code.php

<?php
/**
 * Custom code shortcode
 *
 * This template can be overridden by copying it to yourtheme/woocommerce_email_cuztomizer_with_drag_and_drop_builder/woo_mail/custom_code.php.
 * @var $order WooCommerce order
 * @var $email_id WooCommerce email id (new_order, cancelled_order)
 * @var $sent_to_admin WooCommerce email send to admin
 * @var $plain_text WooCommerce email format
 * @var $email WooCommerce email object
 * @var $attr array custom code attributes
 */
if ( ! defined( 'ABSPATH' ) ) {
	exit;
}
// To include woocommerce shipment tracking details in email sent for order. Link -https://www.flycart.org/products/wordpress/woocommerce-email-customizer
// Shortcode [woo_mb_custom_code type="ph_fst"]
if(isset($attr['type']) && $attr['type'] == 'ph_fst'){
	do_action( 'ph_fetch_shipment_tracking_details', $order );
}

Steps -

1. Place the above code in yourtheme/woocommerce_email_cuztomizer_with_drag_and_drop_builder/woo_mail/custom_code.php
2. Use [woo_mb_custom_code type="ph_fst"] as shortcode