In current FW the Smartknob CAN be used as a slave accessory.
You will get the full functionality of Smartknob if you plug directly into the camera body.
However if you want to use an accessory via 5pin slave cable direct into the 'IN1' Latitude port you can. You just need to plug everything in before you power up the receiver. If you plug Smartknob in afterwards the receiver will not recognise the unit properly.