To unlock the City Heat TT, I have to deploy three different gadgets during one glide attack. I'm using the L stick to target, but it seems all I can do is throw batarangs. Is there an upgrade I need? Or am I not seeing the right controller combos?
Yes, you need to unlock the skills to be able to use gadgets while glide attacking for each of the different weapons. Look at the Gadget Skills section.
Once you have the skills for at least three gadgets, just initiate a glide attack on one enemy (from a ledge, attack an enemy below). Hold the direction toward a different enemy and quickfire the gadgets you unlocked.