Step files are just "dumb" solids and are not useful if you actually want to edit a model's features or relationships. Almost all CAD software keeps the actual editable model info in proprietary file types. Some CAD programs can generate a part file from a step file with varying degrees of success, the professional CAD packages (CREO, CATIA) being the best at it, but even then they often fail to produce a complete part for anything that is remotely complex. Step files are mostly used to export a final product to production (CNC, 3D printing, etc), or sometimes used incorporate common hardware into a larger assembly, like a simple bracket or something.