NanoKontrol is USB, not 5pin DIN MIDI. You cannot connect MIDI controller hardware through USB.

But, first - what you're asking for doesn't require the touch screen at all. I do not use the touch screen to do anything except program custom Performances and, on a gig, select Performances from Live Set (sometimes I use buttons shortcuts instead).

For PART volumes - you can use the sliders.

For PART mute/unmute you have several options. You can use scenes and press a single button to change multiple mute changes at once - and even to change the PART volumes. Or, alternatively, you can use the mute buttons on the right-hand side of the instrument.

I'm not sure why you would feel painted into a corner having to use the touch screen for what you're asking to do.

That said - if you do not like the alternatives - there should be MIDI controllers that have 5pin DIN MIDI ports that will work for you. Primarily, they would need sliders and buttons you can assign CC values to - which would pretty much cover what you've asked for. I'm just not sure it's altogether necessary given you have similar knobs and levers and buttons on Montage itself.

Many people use the Behringer FCB1010, connected via 5 pin din

NanoKontrol is USB, not 5pin DIN MIDI. You cannot connect MIDI controller hardware through USB.

There are adapters, though, i.e.

http://www.kentonuk.com/products/items/utilities/usb-host.shtml

http://www.hobbytronics.co.uk/usb-midi-converter

https://www.excelvalley.com/product/midi-usb-din-converter/

http://compasflamenco.com/midi-c-3/usb-host-midi-2-p-6.html

https://www.juno.co.uk/products/mode-machines-cerebel-usb-to-midi-serial/564328-01/

https://www.thomann.de/gb/miditech_usb_midi_host.htm

it's also a feature of the iConnectMIDI4+ though that also does lots of other stuff

The well-endowed, well-lit, well-laid out front panel of the MONTAGE is worth spending time learning to use, (particularly before investing money and time on an external control device). Only after exhausting the options available need you even consider an external interface.

Seeing the light...
I think anyone who has crossed that hurdle of knowing what the lights are indicating at any moment, knows that it is something that comes only with time and a bit of effort. At first, you find the lights troublesome because you’re not sure what they mean. Later, there is an ah-ha moment when you start to, forgive the pun, ‘see the light’. Exactly, when it happens depends on your own personal workflow.

Once you get to the point where you’ve dropped into Edit enough times, you realize how you can [SOLO] a single Part from among many Parts in a Performance, then you can [SOLO] an Element or Operator within that single Part... and that you can know exactly what your looking at and where you are by the lighted buttons alone.
That’s a point at which you give yourself a Merit Badge for reaching a comfort zone with navigation.

Try to pick up a skill a week... especially those where navigation is concerned. The front panel lighted buttons give you access, not only to the deeper levels of the synth architecture, they also function as the key to the built-in digital mixer. Even when the screen is showing other things, the lighted buttons can let you navigate and operate mixer and synth functions in real time. You can continue to *select* Parts, make changes, adjust the sound... The only way you reach a comfort level with this, is a little at a time.

First step, is to recognize there is a method to the madness of every lighted button and what it is trying to tell you, and knowing exactly what each is attempting to tell you is just a matter of continuing to use the system... and observing what lighted buttons change with what you may have gotten stuck using the screen for...

I mean, who knew... you could operate and navigate most everything in Category Search without ever touching the screen?
(I am just happy folks discover any way at all to use this feature, as long as they learn to use it). But most every thing you can do in the screen can be done with buttons, sliders, Knobs, and other controllers...
Who knew... you could select a Drum Kit Part and make just the snare drum louder without touching the screen.
Who knew... you could select the guitar Part and not only fully EQ it, but Pan it, change the Effect Sends, Edit it... access to as many as 32 parameters per Part... all front panel stuff...

Second step, is to operate as you’ve gotten used to thus far, but try to observe the change in lighted buttons when you find yourself making selections in the screen.

Third step, asking yourself “I wonder why not?” and “I wonder why?” as you explore the synth engine.