Is it possible for the same locomotive to be part of more than one consist?
In the strictest sense, no.
Nor would it be a good idea to do so since you could never be sure who is controlling a particular locomotive.
It is possible to join one consist to another in what is called nested consisting.
Suppose I want to use a locomotive as a helper to get trains up a steep grade.
I would need to form it into a consist with several different main line locos.
Is it possible to set up several consists (each made up of the helper plus one main-liner) so that I can select the appropriate one when I need it, rather than continually creating and dissolving consists each time a main line train reaches the foot of the grade?
If the helper locomotive is an individual engine, it would have only one address.
When a mainline train approaches the gradient, the helper would be coupled to the train and then the helper's address would be MU'd to the mainline train's consist.
In this case, the helper's address is the address which is added to the mainline consist address.
Once at the top of the grade, the helper would be released from the mainline train's MU and also released from the particular throttle used by the mainline operator.
This would free the helper locomotive address, which could then be picked up by another operator who returns the helper back to the bottom of the grade.
If the helper locomotive is a group of MU'd locomotives, very typical of the diesel era, then the helper would have an MU consist.
This consist would be identified by its TOP address.
The mainline train would also have an MU consist, controlled by its own TOP address.
The helper locomotive consist would be MU'd to the mainline train's consist and the gradient taken, controlling all locomotives from the mainline train's TOP address.
At the crest of the gradient, the helper consist would be released.
In this case, the TOP address of the helper consist (no matter how many locomotives are in the helper consist) is again used.
When using a DT400 throttle, either knob can be used for both the mainline and helper locomotive consists.