Hi Hanumath,
Your scenario looks fine.
It should work. Add elements again in target XBO with [Reference].
e.g
[Reference]element FromPOItem;
As far as I know, there are only two XBOs relevant for extension.
1. ConfirmedInboundDelivery.XBO -> Post Goods Receipt
2. InboundDelivery.XBO -> Inbound Deliveries
Best Regards
Fred