MMORPG with enhanced input

Good afternoon. I am interested in learning how to control the game in a way that is similar to classic MMORPGs, but with enhanced input. There are often dozens of keys in these games, and I don’t want to have to create dozens of different input actions. What should I do if some skills require me to hold down a key, others require me to press it once, and still others require multiple presses in a row?