This is do-able, but not with the base sim. As others have stated there is no option to map the MFD range knob.
However, I am a cockpit builder and in conjunction with MSFS I use FSUIPC7.
With FSUIPC7 all of the key bindings are done outside the sim and FSUIPC7 provides access to a lot more cockpit interactions. I believe this can also be done with Mobiflight, and possibly SPAD.neXt
FSUIPC7 has an addon module called a WASM module. This expands the list of available interactions.
Using FSUIPC7 also has the bonus of being able to backup all of your key bindings so if you need to reinstall the base sim you don’t lose them.
This is how my key binding for the MFD map range is shown in my FSUIPC7 ini file
|5=PG,9,C33126,0 |-{:MobiFlight.AS1000_MFD_RANGE_DEC}-
|6=PG,8,C33125,0 |-{:MobiFlight.AS1000_MFD_RANGE_INC}-
You will notice that I use a Mobiflight WASM module. This is because Mobiflight worked out how to do it first but I believe the FSUIPC7 guys have since written their own module. I just haven’t downloaded it.
I have this assigned to a rotary knob in my cockpit and works perfectly.
Stinger