Fortnox - Set custom ordernumber, add this to "YourOrderNumber" in Fortnox

functions.php

<?php
/**
 * @snippet       WooCommerce -Fortnox - Set # infront of ordernumber, add this to "YourOrderNumber" in Fortnox
 * @author        Redlight Media AB / Christopher Hedqvist
 * @compatible    WooCommerce 8.0.2
 */
function redlight_fortnox_order_ordernumber_prefix( $orderData, $order_id) {
    $order = wc_get_order($order_id);
    $orderData['Order']['YourOrderNumber'] = $order->get_meta('_custom_order_number', true);
    
    return $orderData;
}
add_filter('obj_fortnox_order_data', 'redlight_fortnox_order_ordernumber', 10, 2 );