I think it should be possible to remember what my personal train is if I add or remove wagons. It should be doable using the on_train_created event. Would be nice if I didn't have to re-set my personal train when I want to have a wagon for a short while.

Adding this feature will also make the mod compatible with Vehicle Wagon 2 which changes wagons when you load and unload vehicles. For the case when the personal train is split into two pieces, you would update to use whichever half has a locomotive.

You could also remember the entity.unit_number of the personal train locomotive, which never changes even when the Train ID changes.

cool and simple mod compared to others mods doing same or near same but vehicle wagon compatibility is must have for me so please update this :)