How to create DraftOrder with line item property as Hash (nested JSON)

[jankadlec]

I can see some Apps are adding to cart product line custom attributes, that are than copied to final order lineitem properties. I can see they are able to put there nested structs:

that are than copied to order.

When I try to replicate that with DraftOrder API, I cannot, as the lineItem properties is declared as array of key-value, both being string.

Is there another way how to create draftorder trough API with line item properties with JSON as a value please?