Technically, they exist for Ideal Air Systems on the SDK layer as you can see here. However, they are not implemented on the detailed HVAC templates, mostly because it is pretty easy to get the same exact result of heating/cooling availability schedules by creating heating/cooling setpoint schedules with extreme setpoints. It’s also just challenging to implement heating/cooling availability schedules in a manner that works for all of the HVAC templates since many of them have different types of plant equipment. If you badly needed implemented with availability schedules, you can always edit the OSM with a few lines of the OpenStudio SDK like what you see here.