I think all it does is keep track of the cumulative mileage of each defined trailer.

 

^^^this

The truck has no idea what trailer is back there. There is no unique identifier in a trailer circuit to distinguish between a dump trailer and a TT. It just knows when there is a complete circuit in the system. It just lets you know how many miles on trailer A you have accumulated.

I know what you're saying though, it should remember the gain at least when you select that trailer. However it's probably due Ford wanting you to each time assess the load before setting the gain. Probably better and safer, but less convenient.

 

I understand that it doesn't know what trailer but when you name and select a trailer, I would expect it to remember the setup for that trailer.
My radio remembers what station is on preset #3.