Instead of sending the SK in 2 AT commands (KU and then KL), is there some AT command that allows it to be sent as one command?

Instead of sending the SK in 2 AT commands (KU and then KL), is there some AT command that allows it to be sent as one command?

There is no command which sends both parts automatically, they must be sent individually. Also, it doesn’t matter which order they are sent, as long as both parts of the key are received by the endpoint, encryption will be enabled automatically.