Larian has always supported modding and D:OS 2 included a GM Tool, but BG3 belongs to WotC/Hasbro which likely limits what Larian can allow players to do, officially. My assessment comes from many years of watching how Swen and Larian treats players and how WotC/Hasbro treats players. But, if you enjoy snarky cynicism, I am not going to piss on your birthday cake.