Fairly easy. Don't overthink.
Leave both tanks open.
Set the pointer to one tank and leave it there. The window will show green. That is your primary tank.
Use propane as needed and check the window from time-to-time.
When the window shows red, flip the pointer to the other tank.
Refill the tank that was the primary tank.
When you use up the current one, switch to the refilled one.
Repeat as needed.
TT 2015 19RD "TheJayco"
TV 2003 F-350 "Montblanc" - Housebroken chore truck
Sitting in The Cheap Seats.
And proud of it!