Visualize file relations

I'm desiging an interface where file relations are a bit complicated and I could really use some help on how to visualize them.

Basically, it's a programme where you can change different kinds of parameters of trains. The problem is that one train file contains loads of other files (speed etc.), and these files can also be part of other trains. How can I show the relation that one file is part of two or more trains?

Many Thanks, Hannah