Software is more of an operating engineer, i.e. changing the state to accomplish a task.
Most of what people think of for an engineer, is someone using material properties to do something useful.
IMO concentrate on how to do your job/task/hobby to the best of your ability and learn new things to do better, and it doesn't matter as to the label under which you do.
The long trains you mention are called unit trains. They move from point A to point B as one unit. Typically the unit trains will be of all one type, e.g. tank, grain, container.
The trains with mixed types can be unit trains but they can also have intermediate stops where cars are added or dropped off.
The optimizations the rail companies perform to maximize the freight movement (and profit) is very interesting.
and if you can find:
POSITION CLASSIFICATION STANDARD FOR
ELECTRICAL ENGINEERING SERIES, GS-0850
ELECTRONICS ENGINEERING SERIES, GS-0855
TS-3 February 1971
It has good information on what level engineers are working.
I think you have the correct frame of reference, senior level positions are those who are used to handling projects/questions without guidance from others (although most senior folks are willing to ask questions to learn)
Most of what people think of for an engineer, is someone using material properties to do something useful.
IMO concentrate on how to do your job/task/hobby to the best of your ability and learn new things to do better, and it doesn't matter as to the label under which you do.