Some rockets come down in multiple segments, for example a nosecone that comes down on it's own parachute. This can be approximated by putting the nose and the associated parachute in a separate stage, but there isn't a good way to have them separate at apogee besides adjusting it to separate at a certain time in flight. Adding stage separation options for apogee and at a certain altitude during descent would make simulating complicated recovery systems with multiple sections much easier.