With my Google Fu skills, I managed to find a thread over on RCGroups from about 3 years ago, in which someone was using an MZ-24, which, I'm assuming (and possibly incorrectly, as I am not familiar with Graupner radios) that it is a very similar platform to the MZ-12 transmitter, just more channels.
What Graupner posted is thus:
"If you are fine without a wireless connection than you can use the standard 3.5mm plug that comes out of the HW dongle directly with the DSC port on your TX.
All you have to do is configure your PPM and set the trainer mode to DSC-S and you are good to go with any sim I am aware off."
I would guess you'd need a cable/adapter that looks like this:
https://www.amazon.com/dp/B06Y1H8LSX/?tag=lstir-20
Unfortunately, Graupners aren't in my wheelhouse; I know more about Spektrum (I use a USB wireless dongle from OrangeRX that bound like a new model to my transmitter) and have had great success with getting my DX6 and my dad's DX8 to work with Liftoff and AeroFly on the Mac...