In the new era of gravitational wave (GW) astrophysics, a major outstanding challenge is how to observationally infer the formation path of individual binary black hole (BBH) mergers using gravitational waves (GWs) alone. I will illustrate how different formation channels, i.e. formation paths, give rise to phase shifts in the GW signal that can be used to infer the origin and precise dynamical formation of individual BBH mergers. I will in particular describe the case of GW phase shifts arising from chaotic triple BH scatterings that are known to take place in stellar clusters. Modeling and looking for such modulations and shifts, i.e. deviations from 2-body isolated vacuum inspirals, will start to play a key-role in the coming years when the GW sensitivity goes up.