It's called "consisting" Tony, in both the real and model railroading worlds, as far as the US is concerned. Britain, Aus & NZ call them Bankers, 'cause they were used as extra engines on Banks (Grades). You've got NCE DCC now, so you can choose between 'old style' or the better 'Advanced' consisting'. The Old Style is just building consists by adding locos together without specifying which is the lead loco. One disadvantage of the 'Old' is all locos will have their headlights on, and if they're sound equipped the various sound features can't be assigned to an individual loco in the consist. i.e. lead loco only, in control of lights, horn, bell. With 'Advanced', the lead and tail locos are entered first (the NCE Cab asks that, when beginning to build one and the direction it will be running, so if you wish the rear loco (or any within) can be run in the reverse position and run that way around along with the others all running forward.) Once the front and rear locos have been chosen, you then add locos in between. You don't need to specify their exact position, but I usually start with the nearest to the front and work backwards. Once the consist has it's last loco entered, press the Prog/Esc button (key), it should show the lead loco's ID#, if different, select the lead by it's number and enter, and the consist shows as CON XXXX by whatever that loco's # is. The consist # (127-1 the highest being offered first, then working backward as they fill up) is held in CV19 in each decoder. The consist can be run by either the lead's #, or by the consist#. You can then build another if you want and that will record as CON126 and be run by that CON#, or preferrably it's lead loco#. You can add locos and delete locos easily, change which is the lead and/or tail as/if needed. The information on how can be found in the manuals under the heading "Old and Advanced Consists Explained".
I have run up to 6 in a consist with my HO's, divided into a lead group and mid train, all as the one consist, even did it with a 3-2-1, but that was a bit tricky where a train was going down grade at the front and the others still upgrade, and worse when the roles got switched. A bit of an experience with train speed control, which unfortunately doesn't mimic reality.. Have yet to try adding helpers in to a consist as I'm suggesting, but will give it a try next weekend (not this) when we have a Friday night and Sunday day runs, see how that goes.
To answer your concern about messing up locos in a consist. The CV that controls consists in a loco's decoder (that's every individual decoder) is CV19. It can happen, and does with me on the club layout where there are several trains operating at once, that short cicuits can scramble 1 or more decoders in the consist, and they stop receiving commands (they go into a phantom consist). Unfortunately it means identifying the ones affected by physically seperating them and finding which are not responding to the commands. Each of the non-responders can be fixed using the Cab to access each seperately in POM (Programming on the Main) mode. This can be done without affecting other locos on the tracks. All locos need to have their individual addresses assigned for advanced consisting to work.. Select an offender by ID#, enter, to show that # on screen, and then press the Prog/Esc button at the bottom left of the Cab. You'll be asked "Prog loco on Main?", Press Enter. "Prog XXXX? Press enter. The next screen will give you 3 options. #1, Address. #2, CV's. #3, Config. Press key2 on the Cabs buttons, this will show, Select CV - - - -. Write 19 and enter. Next will show Select Value, Write 0 (zero) and enter. The loco should respond with whatever sign the maker has designed for acknowledging CV changes. (jerks forward, toots horn or whistle, flashes lights as appropriate) That will tell you the change to the setting has been successful. You can now select and enter that loco's address and add it back into the consist. Repeat with any other individuals that need it.
Very tedious, but it will be quicker than reading this. (not mentioning how long it might take to remember and apply
) Being as you are in the main a lone operator and thoroughly expert in track laying, should never be needed. This is also how you get a loco out of consist, if you have cleared (killed) the consist from the base station, and have removed the locos beforehand. They won't respond to commands till that's cleared.