A knob can have a MIDI CC or SYSEX set. Provided you have a 'Patch Automator' module, that Patch-Automator will send MIDI CC data when the user moves the knob.
The MIDI data is sent from the audio processing thread, so strictly speaking the GUI itself does not send the MIDI data.
There is I think a DH module that can send MIDI directly out a hardware MIDI port, bypassing any VST host. This can be useful for controlling hardware synths.
Hope that makes sense,