As you can see, it has 2 of each terminal. The supplied wiring diagram only shows one being used. I have two identical 24v strips that I want to dim together - can I just wire them both in?
Yes as long as the total power draw (watts / amps) doesn't exceed the controller or the power supply you're using.
You could plug two in even if there were only one set of terminals. You're wiring them in parallel.