Ok, here is a zoomed out picture of the panel.
So that "VOLTS READ" switch is not a selector, so no center position. It is just an on/off type switch.
In the top right corner someone has added an analog battery test switch, which is what you may have been hinting towards.
Switching the volts read switch does not appear to do anything. However I was on shore power though when I was trying to figure it out and I did not get around to tracing the wires on the back of it. I just figure if someone else had one, they could educate me.