Assigning a button to HDG V/S - TRK FPA mode selector

Hello,

I would like to assign one of my controller button to the A320 FCU button that switch between HDG V/S and TRK FPA modes (in order to easily display the BIRD on the PFD).

I cannot find an option to do that from the Settings menu, but maybe there is a way to do that from a configuration file ?

Thanks a lot for your help !

So it is not possible to assign a button to a control other than the ones listed in the Settings UI, even using a configuration file ?

Thanks for your help.