I have 5 different trailers and the F150 Smart Trailer feature is great for keeping track. Only downside is if you trade in, or something happens to the truck and you forget the mark down the accumulated miles. You also need to have a trailer actually plugged in to access each trailer to get those miles.
Been there, Done that. :) The 2018 I have now will detect when connected and disconnected, but not know which trailer is connected, so one must be diligent in remembering to verify the trailer setting matches if there is more than one.