Three Bonus Skill Slots, Only Two Bonus Skills Available for Purchase
My lingot store only has "Idioms" and "Flirting" both of which I've bought. Is there a third that has to be unlocked from somewhere?
As connorhay12 said, there's the Christmas skill. It only displays at Christmastime, but if you really want it now, there's an explanation of how to get it (it's not gone, just hidden from the store--you're still buying it for lingots) here: https://www.duolingo.com/comment/4997475