To import our orders we make a new Quotation,
save it, select it from the list,
export it with only the ID field,
copy that ID and the orderliness received from the client into a prepared excel that matches the SKU's of products with their ID,
export it to CSV,
go to Favourite/Import records,
upload the CSV,
test it,
and import it.
This seems like a very roundabout way to work with CSV's.
It would help to see the external ID already when editing the SO, or in the list of Quotations.
Using Odoo online with Studio