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add_action('marketking_order_split_created', function($order_id){
    $order = wc_get_order($order_id);
    
    if (!$order) {
        return;
    }
    
    $parent_id = $order->get_parent_id();
    
    if (!$parent_id) {
        return;
    }
    
    $parent_order = wc_get_order($parent_id);
    
    if (!$parent_order) {
        return;
    }
    
    // Copy meta data
    $meta_keys = [
        '_billing_wooccm14',
        '_billing_wooccm13',
        '_additional_wooccm0',
        '_additional_wooccm1',
        '_additional_wooccm2'
    ];
    
    foreach ($meta_keys as $key) {
        $value = $parent_order->get_meta($key);
        if ($value !== '') { // Only update if value exists
            $order->update_meta_data($key, $value);
        }
    }

    $order->update_meta_data('is_child_order', 'yes');
    
    $order->save();
}, 10, 1);