Default Sales Order Source Type not available on sales order

Summary:

How to default sales order source type in Sales Order?(Internal and External)

Use Case:

when we dont have a stock it should trigger a requisition, but as we know we have a option to give supplier name and site which will create the req.

But the Customer Support team doesn't know which supplier to choose from..so it should give them flexibility to choose the Source Type just like EBS

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