How can I modify all fields of a Child Motion of a Blend Tree through Script?

When I create child motions for Mecanim blendTrees
blendTree.AddChild()
I only have access to the motion and threshold.
If I try blendTree.children it seems to only be a copy?
So…
blendTree.children[0].timeScale = 2f;
doesn’t work.
Is it possible to get access to blend tree children through script and modify other fields?
Thanks!

Same issue here
Im trying to edit the threshold through an editor script
Does blendTree.AddChild() work?
@CAS_Kicks
Did you get it working?