Barn3 switch

I am a little confused by your nomenclature.  Imagine you have an H9 with a Barn 3 switch attached, slide switch to the rear.  From left to right top to bottom, what are the footswitches named?  The apparent order of the switches does not seem to line up with logically with H9 control app. Finding a firm setup is hunt and peck and cycle power at the moment. 

You should set up their functions under Pedal Settings -> Aux Switch Mappings, and you can assign Tip/Ring/Tip+Ring accordingly. 

Please read this to find out what option you should use to assign each switch:

https://static1.squarespace.com/static/539f0880e4b0e0318ea3192f/t/5940029fb8a79bde2d979ab5/1497367242457/OX9-Manual-2017.pdf

With the switch up (rear? proably):

Left: Foot Switch 2 (Ring)

Right: Foot Switch 3 (Tip + Ring)

with the switch down:

Left: Foot Switch 2 (Ring)

Right: Foot Switch 1 (Tip)

Hint:

If you don’t use expression pedal or additional foot switch, you could use OX9 and map all 3 buttons.

Turn the switch down (towards you, expresion pedal position in the documentation).

This way you would have:

Left: Foot Switch 2 (Ring)

Right: Foot Switch 1 (Tip)

Both: Foot Switch 3 (Tip + Ring)

Trivial, but not covered in the documentation. Works well for me in the minimal setup.