Looks like you can no longer add your Known Traveler number to a reservation.
Does this mean that UA will be transmitting the info based on your stored/updated MP info, so there's no need to be able to add it to records, regardless of what shows in the reservation?
If so, that's a good thing. When I got my Global Entry, I remember having to manually update my UA reservations. DL, OTOH, let me add it to my profile and it updated all my ressies automatically.
It would be nice to confirm the design, which hopefully is that any UA reservation with your MP on it will transmit your full name as stored in your MP profile (irrespective of what shows on the ticket) along with Known Traveller info.