Creating an order without specifying the property options.allow_separate_shipping will not have the shipping section of checkout visible and the shipping_address of the completed order will always be the same as the billing address.
With this order configuration Klarna Shipping Assistant (KSA) is disabled.
As a merchant you can provide Klarna with shipping_options you want to present to the consumer. These are sent in using the property shipping options . This will enable Klarna Shipping Assistant(KSA) which will present a shipping selector in the checkout where the consumer can select a shipping option and the cart will be updated automatically.