Those battery 'level' monitors.....well they are just 'bells/whistle' for salesmen to point to for the 'ahh ooh'.
When plugged in to shore power the on-board converter should be charging/maintaining camper battery.
Just need to monitor battery water level to get an idea if converter is overcharging.
Look inside your DC DIST Panel where all the fuses are...probably in same panel as AC Circuit Breakers....and find out WHICH converter you have.
Good converter with 3 stage charging will maintain battery
Unplugging from truck.....
Your F150 'isolates' truck/camper when ignition is OFF so camper can NOT run truck battery down when truck is not being used.