If a discrete code exists, the Harmony can use it. It would more than likely already be in the Harmony database, but if it isn't, and you can find it in Pronto hex format, you can add it to the database.

If a discrete doesn't exist, you're still in luck because Smart State keeps track of inputs even using toggle commands. eg if you are in an activity that uses "Input 2" and you select a new activity that uses "Input 5" it knows it need to send 3 "Input toggle" commands to get to the input you need.

You can set it up to use input toggle commands, bring up and select inputs from a menu, or use discretes...whatever is available.

Basically, when you set up the remote you tell it what devices you want in each activity, what function they perform(volume control, video display, passthrough etc)and what input they need to be set to. Then when you select an activity it makes up it's own "macro" on the fly to get the devices from their current state to the state required for the newly selected activity...ie turns devices on or off as required and sets everything to the proper input...even if they don't have discretes.