If the requirement is to set the shipping method,then in SCA an frontend API is available.
Sets shipping method for order.
Parameters
shipmethod[required] {Object with values for fields}shipmethod[required]shipcarrier[required]Note Valid values that can be set for shipcarrier areupsornoups.
Returns
No value returned.
Supported Domains
Checkout
Example:
var field = ModelsInit.order.setShippingMethod({“shipmethod”: “1788”});