by EngineerJohn » Fri Jul 10, 2020 5:25 am
Open up the scenario in the editor from the main game menu, place your new lead locomotive alongside the old one, and you can drag all of the icons over to the new loco from the existing one in the scenario. Then delete what was the original lead loco for the scenario, put yours in its place, and that replaces the lead loco. The rest of the locos and rollingstock in the consist can be deleted and replaced too but make sure you check all of the driving instructions to make sure the lead loco and rest of the consist is referenced correctly, or else the game might be looking for the old stuff and not recognize your replacements giving you a checkpoint failed unintentionally.
Hope that helps. I do that nearly all the time.
“A designer must always think about the unfortunate production engineer who will have to manufacture what you have designed; try to understand his problems.” - Raymond Loewy