TL;DR - check the
Indigo IOM documentation when you want to access properties/states of built-in device types. Read on for more specific information.
Device types that are directly implemented by Indigo often don't have custom states, because they are not custom devices. Plugins can implement any of the device types Indigo supports or they can define a "custom" device, in which case Indigo shows them in a list. Plugins can also add "custom" states to devices that implement one of the supported classes.
For the standard device definitions, the properties and states for the device are documented in the
Indigo IOM documentation. We don't expose them in the Custom States tile because they aren't custom. The original intent was for built-in devices to have direct properties (i.e.
my_device.fanMode) and that the states list would be used for things that were custom to the specific model of the device. In practice, and over time, it's become less clear about the distinction between properties and states. Perhaps something we'll address some day, but it would be a big fundamental change so it's not likely to happen soon.