Mine has that exact valve and yes it is an auto changeover valve. Currently yours is pointing to the left (drivers side)and that is the tank that it will draw propane from. When the sight glass goes red that tells you the left side tank is empty and you are now drawing from the right side tank.
As stated above, once the gauge goes red,
turn off the tank that the lever is pointed to. In this picture turn off the left tank.
flip the lever all the way over to point at the right tank. The gauge should go green.
Remove left tank and go get it filled.
Place left tank back on trailer but leave lever pointed to the right until that tank empties.
I notice though that your sight glass looks to be half red and half green. My original valve did that same thing and I was always bothered by it. In the manual and on line you will read that it will be either green or red, not somewhere in between. I finally reserved myself to the fact that if it's showing green at all then all is good, because when a tank ran out it definitely went red.
Eventually the regulator started leaking and I bought an exact replacement for $40. The new regulator goes full red and full green.