I’ve found a couple of packages that are used, there undoubtedly are more, to plan model railroads, AnyRail, and 3rd PlanIt.
AnyRail is an entry-level tool designed to provide the ability to design layouts. It has several libraries of track to choose from and has some building footprints. I have found it easy to use and was able to get up to speed quickly. The license is inexpensive also.
3rd PlanIt is a CAD (Computer-Aided Design) tool that allows you to design the entire layout including benchwork. It is harder to use than AnyRail but has a lot more features. I plan on using this software to design the entire room. This will need to wait until I have a much better idea of the exact size and shape of the basement once it is finished.