Animation Blending

I’m looking for an example of or a source text file of a .state_machine file that has multiple animation layers/nested animation layers (I think), as well as, how to transition between these layers and it’s child states.
What I am trying to do is have multiple animation events to be able to played/triggered at the same time such that if a character mesh is in the walking loop it can also trigger an event to perform actions with arms and upper torso.

Not sure why this go bumped with no posts but I’m going to assume it “needs-more-info”.

This video is what I’m wanting to do, Animation Combining/Blending.
I’m not an expert with the jargon but I think the question I’m asking is, “how do I define, the combining of animation layers in .state_machine files?”.