Ground Handling Dataref and set-file

Hello everybody,

I've been dealing with Ground Handling Deluxe from JarDesign in the last few days and trying to create my own settings. So far it works quite well. But so far it has not become clear to me what you can do with Dataref = non in the set file. From the video tutorial by JarDesign, I can't figure it out.

Here is an excerpt from an original file from JarDesign:

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#New Car for this set:
01 type_name=GPU
21 dataref=sim/cockpit/electrical/gpu_on
#Route details:
02 step_nomer=0
03 x_coordinate=1.8
04 z_coordinate=-20
05 heading=180
06 speed=0
07 a1=0
08 t1=0
09 a2=0
10 t2=0
11 a3=0
12 t3=0
13 a4=0
14 t4=0
15 a5=0
16 t5=0
20 DRFvalue=non
02 step_nomer=1
03 x_coordinate=1.8
04 z_coordinate=-20
05 heading=-nan(ind)

In this case, what does the entry: 21 dataref = sim / cockpit / electrical / gpu_on do?

I also want to control various set files while running X-Plane 11. I imagine it like this: A set file for handling with gate and a set file without gate, i.e. with stairway. I would then like to be able to select them accordingly. I didn't find a solution for this either. Maybe that somehow works with FlyWithLua?

Thank you for answers.

Coverdale