Question: Customising Sales Order - multiple orders under the same number

Hi Friends
Looking for direction, the ERPNext way/approach if you like, I want to have multiple orders under the same order number created all in Sales Order module. I already have a sales order module the user can add order items all bundled under the same product delivery date. Now I would like to give the user the option to add many( with no limit ) orders under the same number, each have its own product delivery date. I am open to suggestions and best practice.
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