I dont know who needs to see this, just wanted to share a solution for a problem I encountered recently. I hope it helps someone.
Lets say you have an object House and inside that House you have another object Chair in a very specific spot. you scale the House's Size by 2, making it bigger. The Chair then is not at the same spot inside the House because the House's size is different. you need to move the chair to that very specific spot without doing it manually.
EDIT Moved the solution to an answer
this is the formula you would use: ( (Chair.position * House.scaleFactor) - (House.position * (House.scaleFactor - 1)) )
In Threejs code it would look something like this:
const scaleFactor = 2;
house.scale.setScalar(scaleFactor);
chair.position.set(
(chair.position.x * scaleFactor) - (house.position.x * (scaleFactor - 1)),
(chair.position.y * scaleFactor) - (house.position.y * (scaleFactor - 1)),
(chair.position.z * scaleFactor) - (house.position.z * (scaleFactor - 1))
);