Tried using click and drag in the VC ... it works
Looks like all the XP11 key bindings for changing the Barometer setting are applied in a different way to when using 'click and drag' with the mouse.
So, using the key-bindings looks to be only changing the Altimeters read out, not the Barometer directly... If i set the aircraft's indicated altitude using the bound buttons, then use click & drag. Moving the Baro reading by 1 increment (or more), the Altimeter rapidly changes back to the reading set with the mouse.
Does the 340A have custom key-bindings for the Barometer? Have looked, but didn't notice any.