Use Add Object -> Plug In to add Kontakt VST to Cantabile. Go to Tools -> Audio Ports to add a second Stereo out (here it’s Drums 2). Starting from the top, there are 2 routes, one for MIDI ch 1 and one for MIDI ch 2. The destination for both is Kontakt, but different MIDI channels. Then, in Kontakt, I added a Stereo out so that “Garage Kit” goes to st.1 and Drum Lab goes to st.2. Likewise, Garage Kit listens to MIDI 1 and Drum Lab listens to MIDI 2. MIDI input comes from the default MIDI device “Main Keyboard”. This doesn’t have to be a keyboard, just whatever your main MIDI device is.
So, for Cantabile you have to create an second Audio out port, create your Routes, and instantiate Kontakt. Everything else is done in Kontakt.
I think this picture is going to show up really small. Hopefully you can zoom in. Does this help?