This is one of those dark arts things.
The simplest way is to check-in and use baggage/ lounge benefits on your preferred program, and then switch to the other program at say a gate desk, and get the boarding pass reprinted.
A few agents who know Amadeus (the booking system of most oneworld airlines) may actually be able to tag separate fields (there are four FYI)
https://www.australianfrequentflyer..../amadeus-fqtv/