Do you mean by completely custom bodies which only playable character use? Nope. But if it is just edit of existing body then it is not something which no one figured out. The problem is if you edit existing body model it will affect all NPC and characters who use the same body model. So, the best solution would be to edit STRONG body type instead of thin one since not a lot of character in the game use that body type, but now there is another damn issue: all outfit models in the game has been made for thin body type and use some specific bones scaling to fit correctly to strong body type in the game which make impossible to just import outfit model into 3d modelling software and make it fit to your custom strong body model, because you dont know how to scale bones to compare models. People in Larian studios discord aren't interested in editing body models, so I don't think we will see some tool which can convert/scale outfit models from thin to strong body type and back.