Say you setup a new key that is activated by pressing Space Bar. It only has one step. That step is to send, say, 1, 2, 3, 4 and 5 to each window. Now you go into Rift and setup 5 different abilities in the 1-5 spots. Now, when you hit Space Bar Rift will ALWAYS try and do the 1 ability first. If it's not available or is on cooldown, it does 2. Then 3 etc. In this way you can place cooldown-locked abilities that you ALWAYS want to do first. It's basically a perfect priority system.