Is there any way to assign a short cut (combination of keys) to a button for the Yoke One ? I am trying to apply the short cut for the FSKneeboard app but that of course isn't a function within MSFS so I cannot map it to the yoke in MSFS - and outside of MSFS the yoke is just considered a regular game controller which I can test or calibrate but afaik not map buttons for. 

Any good advice on how to get this done ?

If nothing helps I guess i will need to use VoiceAttack, but I would prefer to map it to a button (one program less to run when simflying)

This questions might be better answered in the Hardware controller forum since it is probably not necessary a Fulcrum issue.
There are a few tools like JoyToKey that might be able to couple a button on the yoke to a keypress. Ideally, FSKneeboard could have an option to open by using a joystick button.

As an alternative you could buy something like the Legato Stream Deck to start and control any number of applications.