You can teach to any key you want to. You should pick out some unused keys, in a convenient configuration, and learn the missing commands on them. Unfortunately, there are no titles for what you want to learn, so you will just have to remember, or write down, what you learned and where.

I am assuming that the Amplifier key on your Elite remote is just a shift key, and doesn't send a signal, so press it, then put the 2500 in learn mode, press the key of your choice on the 2500, and then press the key(s) you want to teach to the 2500 from the Elite remote, and you should be able to learn the signals.