Like ElectroBoy and others have said, Jackery does pass-through charging well. (Bluetti claimed to and we almost lost 5 days worth of food on way out to Death Valley. Luckily saw the fridge had an error midway on the drive. This is what prompted me to switch to the Jackery.)

If you do the add-a-circuit to keep the 12v hot, you could leave the Jackery plugged into the rear 12v and it would charge all the time until it was full as it tapers off the power automatically. My fridge draws around 35-40W, which is around what the 12v outlet outputs so the Jackery would hardly need to pull power from the truck to keep the fridge maintained once at temp.

Side note, the Rockpals folding solar panels are a nice way to keep the Jackery powered up during the day again using pass-through. Mine put about 74W to the Jackery in ideal light.