amp_earn_exp returns four things, one of them is all moves the monster could potentially learn if it levelled up. You'd need to do something similar to what the battle win state does: store the list when earning EXP, extract the moves specifically, and then have a loop where you take one move at a time, spawn a menu asking the player if they want to learn that move / learn it directly if there's room, and when the menu is destroyed, move on to the next thing from the queue (or proceed if the queue is empty)
