hhhm. Its not so easy at all time.
Specially for AddOn Aircrafts as i know its often more difficult.
Please Note: this tool is pretty new. So the List is not complete. With the time more and more users share there digged Datarefs and Commands with us.
E.g. if a AddOn like the Zibo use own stuff then we can not know it (Cause we not own this addon )... But if a Zibo user find out those data and give it to us then we add it to the list.
Basically we can say... Outputs are Datarefs .
In your case... There can be for sure in some AddOn Aircrafts also a own Dataref like "Parking Brake Indication" .... E.g. if there is a LED in the Virtual Cockpit.
Maybe in a good way that Dataref only show 1 (LED on) if also Power is in aircraft ... If Master Battery is off the LED will not light whatever brake is set.
But sure... theres also a Dataref like the above one that show simply the status of the Brake itself (set ot not). We can easy use it now.
For Inputs as i know we can write Datarefs, too ( Not sure if all or just some of them)
So as you say.... In Output it show current state ( e.g. 1/0) in Input we would write Value 1 or 0 to it to change the state.
Alternate are "Commands" ... These predefined Actions are like Makros. Here we would not use a Value... Cause here there would be 2 Commands like "Parkbrake set "and "Parkbrake Release"
I not use Xplane and also not this tool.
Its mor logical to talk to the guys who build it and work with Xplane all the day.
But they are not here in Forum. They are on our DISCORD https://www.mobiflight.com/#hyperlink
Please join our Server and directly get help from the Pros !