Sorry about the delay, got side tracked with stuff.
In the AnimationTreePlayer properties you must assign the AnimationPlayer, then your animations will be available for each animation node you create.
I'm glad you figured it out!
I did not find tutorials how to make a 3D animation to loop, while i finally found there is a button in the AnimationPlayer to setup an animation to loop :disappointed:
Yeah, most of the animation related stuff is pretty much undocumented and some of it is not terribly intuitive.
I hope we'll see more and more 3D games tutorials with setups, because those are missing.
I hope so! There is definitely a lack of tutorials for 3D stuff in Godot, especially for animation.