My understanding is that I replace one of the pots with the 6 pos switch.
My question is how is this identified in OP Config. My thinking is that I would have to use resistors on each position to mark the signal into 6 steps ie from pwm pulse -100% to +100%. Then set this channel in OP Config as a digital chan with 6 positions.
Hi Rock, this method that you described will work with any transmitter and OP Config will be able to read it just fine (as a 6 position digital channel) assuming the resistor values were correctly chosen. As you say, you replace a pot with a 6 position switch and resistors, it basically ends up still being a pot, but instead of an infinite number of positions from min to max, it only has 6. This doesn't require any special transmitter programing, and as far as the transmitter knows it's still a pot. But the transmitter will output 6 evenly spaced PWM values, and OP Config will read those as a 6 position switch if you tell it to.
I have Er9x firmware in the radio and I know you can setup different curves on a analog pot chan to generate a signal at the selected steps on the pot as it is turned. I think these are then described as Logical switches in the firmware 
so not sure if this is a simple method with no mods to the radio but how would these logical switches be detected in OP Config.
This I am not so familiar with. I think what I recall hearing is that Er9x had some functionality to let you adjust the curve if for example your resistors didn't give you exactly the outputs you were looking for. But I could be mis-remembering. Maybe as you say there is some way to program it so that an analog pot would only output 6 positions. Of course then you wouldn't have the tactile feel of 6 positions, but maybe that's ok with you.
I should say that you can accomplish the same effect already without any mods at all and no transmitter programming. Just assign your analog pot in OP Config to a digital channel with 6 positions (yes, we are telling OP Config a lie, but that's ok).
As you move the pot from one end to the other, OP Config will translate all the infinite values into one of 6 positions, by choosing whatever position is closest to the current PWM reading. So again, no tactile feel on your transmitter, but you do get 6 positions (or however many you want).
If I misunderstood your second question you can enlighten me further, but at any rate, the first approach using a hardware mod will work.