Create New Shipment and link it to planned order release

I managed to Plan and Create 5 Buy Shipments from Order release each have planned weight 20 Ton.
The Case Is that I need to create a manual shipment (Number 6) and then link it to the same order release and to have the same itinerary and then to update the order release total net weight to be 120 ton after adding the 6th shipment with net weight 20 ton