Just need to know its importance.
And why are there 2 of these?
The switches are for turning on the power to the x4. It has two because the x4 draws a lot of amps, by splitting it into two switches there’s less amps going through these contacts. The x4 will work if only one switch is turned on but would not recommend that as they are I think made to handle 150amps max, and the x4 draws up to 300amps.
I designed the knob for that switch. It is connected to a resistor which reduces the arcing inside the switch. Arcing damages the contacts and makes it unable to handle the amperage. Turn that knob on first and turn it slow to give the capacitors in the ESCs time to charge.