I have done optical designs the old fashioned way, as I was taught in a college class many decades ago. That means pencil and paper and simple optical rules. Strangely enough, that was very good for things like projector and telescope design but it may not be as good as a modern computer program for something like your bicycle light.
I do not have any recommendations for such a program. I can say that you do want something more then simple ray tracing because you will be using an extended source (the LED) and you want a spread out pattern, not just a sharp image.
But I will say a few things about this.
There are two ways of designing such lights: with a reflector and with a lens. And, of course, both have been used with light sources that are omnidirectional. But LED in general, are not so it is probably one or the other.
Parabolic reflectors are generally the better choice. You don't want the pattern to be too focused because that can blind others. That is a great consideration. But by moving the LED away from the focal point of the reflector, along the optical axis, you will produce a spread out beam. The further away from the focal point, the more it will be spread. Many hand held flashlights operate like this. I have one and it does effectively spread the beam out to illuminate an area instead of just one spot. This is a simple thing to experiment with. All you need is the LED and the reflector and a dark room. The rays trace themselves and you can walk around in front of it and see the results. On, and you can try positions that are moved in both directions from the focal point. They will produce somewhat different patterns.
If you would prefer a lens, it would work much like the reflector. You simply move the light source away from the focal point to spread the beam out, just like with the reflector. If you want a lens I would suggest a fresnel lens. They use concentric zones to flatten the lens and therefore are a lot lighter. Plastic ones can be purchased.
https://www.google.com/search?client=firefox-b-1-d&q=fresnel+lens#cobssid=sIn any case, lens or reflector, you want one that is wide enough to catch all or most of the light produced by the LED. If you have a spec sheet on it, that should show the angular pattern of the light.
If I were doing this I would consider making the LED movable so I could change the pattern while riding. That could be the best of all worlds of bicycle head lights. And voice or thought wave control. And how about servo controlled or gyro stabilized so the light points in the direction of travel even when the handle bars are making small steering corrections? I could have real fun with this.
I don't know if you want to consider it but an easy way to do this would be to purchase a commercial light and modify it to your specifications.