Hello, I'm wondering if I could change the animation (the one inside the red circle) from script. Any idea how? Thank you in advance (Sorry for my bad English, English is not my main language).

It seems to be possible like this:

func _ready():
	var blendTree : AnimationNodeBlendTree = $AnimationTree.tree_root as AnimationNodeBlendTree
        # "BlendSpace1D" is your node name from AnimationTree
	var blendSpace : AnimationNodeBlendSpace1D = blendTree.get_node(&"BlendSpace1D")
	var blendPointNode : AnimationNodeAnimation = blendSpace.get_blend_point_node(0)
	print_debug("Animation is %s" % blendPointNode.animation)
	blendPointNode.animation = &"sample2"
	print_debug("Animation is %s" % blendPointNode.animation)

Thank you but I got an error

I set it in a way it would change the animation after a keyboard Input