The collimation system of the Future Circular Collider, operating with leptons (FCC-ee), must protect not only the experiments against backgrounds, but also the machine itself from beam losses. With a 17.8 MJ stored energy of the electron and positron beams, they are highly destructive, and beam losses risk to cause damage or a quench of superconducting elements. Accurate collimation simulation tools and models are needed to design the collimation system and optimize the collimation performance, including magnetic tracking, synchrotron radiation and optics tapering, as well as particle -matter interactions. As no existing code was found that incorporated all these features, a new simulation software tool has been developed. The tool is based on an interface between a particle tracking engine, pyAT or Xtrack, and a Monte -Carlo particle -matter interaction engine for collimator scattering, BDSIM, which is based on Geant4. Results from a simulation of edge scattering from a beam halo collimator in the FCC-ee are presented to demonstrate the capabilities of the tool.