Except that nowhere in the RAW does it say that you can switch out a trick, unless I'm missing something. There is no mention of an animal forgetting a trick unless you are training them with a new general use. My question was specifically asking for a reference to the RAW that would allow this.
And my understanding of the PFS society rules is that if you acquire a new companion, they only begin with their bonus tricks, not the 3-6 regular tricks that they can learn. So those would need to be learned as usual.