[ShipStation] Export Custom Field Data to ShipStation

wc-export-custom-field-data.php

// Add this code to your theme functions.php file or a custom plugin
add_filter( 'woocommerce_shipstation_export_custom_field_2', 'shipstation_custom_field_2' );

function shipstation_custom_field_2() {
	return '_meta_key'; // Replace this with the key of your custom field
}

// This is for custom field 3
add_filter( 'woocommerce_shipstation_export_custom_field_3', 'shipstation_custom_field_3' );

function shipstation_custom_field_3() {
	return '_meta_key_2'; // Replace this with the key of your custom field
}

NOTE: custom_field_1 is locked to the coupon code(s) in class-wc-shipstation-api-export.php @ around line 149:

$this->xml_append( $order_xml, 'CustomField1', implode( ' | ', version_compare( WC_VERSION, '3.7', 'ge' ) ? $order->get_coupon_codes() : $order->get_used_coupons() ) );

@woocommerce Why not follow the same pattern as custom field 2 and 3, but default the meta key to the coupon code? It'd work the same out of the box and allow developers to re-map the all the custom fields.

Where to find the meta_key? I'm sorry. I'm new to this. I'm trying to export data from Woocommerce "Extra Product Options" Plugin to Shipstation.