Yeah, it really wasn't central to the plot, but I think it was an endearing part of the episode. Oliver Brandt was a member of that genius society club, and yet he still played with 'toys'. And Columbo was so fascinated by it.....it was a very sweet scene.
There was also a very elaborate train set up in the office of Alex the Spielbergish director who kills his old friend who comes to the studio to visit him. He has the backlot street washed down and then electrocutes him and dumps his body out at the beach. Alex is like an overgrown boy with lots of toys and a trainset was definitely one of them.