Each control only sends and responds to one MIDI message. To send more than one message from a control, we'll use supercontrols.
For this example, I set up three buttons: "Superman," "Message 1" and "Message 2."
In Design Mode, double tap on Superman to bring up the properties. Switch to the "relationships" tab.
Now toggle "supercontrol" to be on (blue). Note that the subcontrols button nods invitingly.
Click on "Subcontrols," which brings up the Subcontrols pane.
Now drag the "Drag to Subcontrol" button to each of the two subcontrols (one at a time). The final result looks like this:
Then get out of Design Mode.
Now Superman sends out Message 1 and Message 2. That's it!
You can even hide the subcontrols behind the supercontrol if you like.
By default supercontrol does not send out a MIDI message (though it will respond to them).
With buttons, the supercontrol's subtype takes precedence over the subcontrol's subtype. So if the super is momentary, the subcontrols will act like momentaries.
For knobs, sliders, crossfaders and XY pads, you can invert the subcontrol to reverse its direction.
Of course you can chain supercontrols and subcontrols in many different interesting and creative ways. MIDI Designer will keep you from creating endless loops.
Supercontrols are also the basis of how MIDI Designer handles button groups and steppers (seen in video). Also, the MIDI Designer Pedalboards feature is built entirely on the supercontrol infrastructure.