Well.. You can add meta for original and cloned order. Just add +1 for it, each time when you will clone items.
function create_order( $original_order_id, ...
try {
$new_order = new WC_Order();
$new_order->set_props( array( ...
}
$original_order = wc_get_order( $original_order_id );
$order_item_num = $original_order->get_meta('_order_items_num');
if($order_item_num >= 1) {
$new_order->update_meta_data( '_order_item_num', $order_item_num+1 );
$new_order->save();
$original_order->update_meta_data( '_order_items_num', $order_item_num+1 );
$original_order->save();
} else {
$new_order->update_meta_data( '_order_item_num', '1' );
$new_order->save();
$original_order->update_meta_data( '_order_items_num', '1' );
$original_order->save();
}
Now you can modify order number
add_filter( 'woocommerce_order_number', 'change_woocommerce_order_number', 1, 2);
function change_woocommerce_order_number( $order_id, $order ) {
$parent_id = $order->parent_id;
if($parent_id != 0) {
$parent_order = wc_get_order( $parent_id );
$order_sub_num = $order->get_meta('_order_item_num');
return $parent_id . '-' . $order_sub_num;
}
return $order->id;
}