Which variables are useables as expression in Computed Attributes?

Hello,
with

Driver ID
driver ? false:'Drivername'

I give the attributes for tc_positions. So i can see later which driver was in which car.
But i would like to see there with wich device and which car.

Is there a list which variables i can use as expression?
I am looking for something like:

Driver ID
driver ? false: (deviceID+'Drivername'+contact)

Is somathing like this possible?

I tried looking for this
https://www.traccar.org/search/?q=attributes
And read this
https://www.traccar.org/documentation/computed-attributes/
But didnt find something

You can only use position attributes and properties.

I testet speed (without any Brackets or ' " ´ etc) that works
So i can use every field name from tc_positions, nothing else. Correct?

You can also use attributes from the positions table.

I do it with "try and error"
e.g. deviceid did not work
Is there a list?