Thanks for the suggestion. We haven't made a simulation of the Chicxulub impact because our asteroid impacts don't yet simulate all the parts of the extinction event that you would expect, including having the atmosphere fill with find particles blocking out sunlight complete for multiple days.

We don't really have any secret tools that make it easier to create a simulation like this. The best way to try and recreate the impact is probably to just keep trying to use the Launch option on the Add tool to launch asteroids at Earth at low simulation speeds.

You could also check out the Steam Workshop and see if anybody else has replicated this simulation already.