To my knowledge, there are atleast two possible ways to do this:
1. animationGroup.clone()-function:
If bone names are identical on both skeletons (else you have to rename), the targetConverter would look similar to this:
(target) => {
let idx = skeletons1[0].getBoneIndexByName(target.name)
return skeletons1[0].bones[idx]
}
2. create animationGroup and add animations with targets:
var newAnimationGroup = new BABYLON.AnimationGroup("newGroup");
for (var {target, animation} of importedAnimationGroup.targetedAnimations) {
newAnimationGroup.addTargetedAnimation(animation, newTarget);
}
Playground of carolhmj: