Distribution of GW progenitor events as a function of the metallicity of the parent stellar particle in four different boxes of the MTNG simulations: MTNG46, MTNG92, MTNG185, and MTNG740 (from left to right). The metallicity distribution of the total merger events, along with the contributions from different compact binary merger channels, is displayed as indicated in the legend. All distributions are normalized to the total number of merger events. As in Fig. B.4, the vertical dashed lines mark the value of Z_⊙ adopted in the simulations.