Maybe it could be fixed on user's side before official patch comes.

Open camera.cfg and find "[CAMERADEFINITION.0]"
Then find "[CAMERADEFINITION.1]", then "[CAMERADEFINITION.2]" so on.
Make sure that the number is not skipped nor duplicated.
Manually renumber them when omission or duplication is found.
In my case the culprit was duplicated number.

And of course, always make a backup when you fiddle with original files.

@GunStrauss said in Black Square Analog Baron Fuel Pump Lvars:

I can upload a profile when I get home in a couple of days, may I ask what controllers you use?

I'm not sure what you mean by "controller". I think my answer should be "None".
I have built a cockpit in which I have replicated the pilot's side of the 3D image you see in the Baron in FS2020. So I have physical switches connected to a Leo Bodnar board (BU0836X) and I am using SPAD.neXt to handle the switch inputs for me.

I have been busy researching and have got it working satisfactorily. I discovered that I have to turn on the correct electrical circuit as well as switch the pump on.

“A:CIRCUIT SWITCH ON:4, bool”, and “A:CIRCUIT SWITCH ON:5, bool”

So, for the left pump switch:

“Set LVAR:VAR_FUEL-SWITCH_PUMP_1 to #"; where # is the state of the switch. 0=Off, 1=Low, 2=High.'

and Set CIRCUIT_SWITCH_ON:4 to 1 (or 0 for off)

For the right pump switch:

Same as above except use “Set LVAR:VAR_FUEL-SWITCH_PUMP_2” and

for the electrical circuit use “Set CIRCUIT_SWITCH_ON:5 to 1” (or 0 as appropriate)

Everything is now working as it should.
Cheers!