Ok Guys, there was a bug which prevent script to relay on the correct AnimationGroup to add the node. I solved it and publish a PR related to it. Be aware that there might be a delay for the PR to be merge.
Assuming a Group named “Animation” exist, the following script
manager = dotNetObject “Max2Babylon.MaxScriptManager”
g = manager.GetAnimationGroupByName “Animation”
id = $.handle
manager.AddNodeInAnimationGroup g id