Fortnox - Reference

functions.php

<?php
/**
 * @snippet       WooCommerce - Adds Custom reference on order
 * @author        Redlight Media AB / Christopher Hedqvist
 * @compatible    WooCommerce 4.7.0
 */
function redlight_fortnox_custom_reference( $orderData, $order_id) {
    $order = wc_get_order($order_id);
    $orderData['Order']['YourReference'] = '';
    if($order->get_meta('_custom_reference')){
      $orderData['Order']['YourReference'] = $order->get_meta('_custom_reference');
    }
    
    return $orderData;
}
add_filter('obj_fortnox_order_data', 'redlight_fortnox_custom_reference', 10, 2 );