Hi,
Yes, I have a dedicated OS to control garden lighting, and some zones on my other 2 are also used to control lighting. All you need is a 24V AC relay per individual zone, which you connect in exactly the same way as a water solenoid, there are some details here: https://opensprinkler.com/using-24v-ac-relays-with-opensprinkler/
Make sure you choose a relay with enough current rating to switch the entire load……if you have 600W transformer @12V that’s up to 50 Amps !!!
Or break up the lighting into zones so you can use smaller relays, or even convert halogen into LED to reduce power consumption.
Regards,
Bruce