How to create single invoice for single sales order when order is shipped in two different days

Summary:

Overview of the Issue:
When the sales order shipped in two different days, 2 invoices are being created. Due to which there is payment issues happening in later stages of finance process.
So, Our requirement is to have a single invoice for single sales orders though the sales order is shipped in multiple days.
However we have implemented the orchestration changes in phase1 to go all lines together in Awaiting Billing status, after lines are shipped only. For ex: if order is shipped with few lines on day1, then those lines will be stay on Awaiting Shipping until rest of the lines shipped.