The latest version of the animation introduction explains the 3.1 animation player, but it was never backported to the 3.1 branch. With 3.2 coming out soon it might not be worth it to do that.
I found two minor issues in the Latest branch:
See the animation panel reference below for details.
This links nowhere.
This creates a new track and our first keyframe at the beginning of the timeline:
https://docs.godotengine.org/en/latest/_images/animation_track.png
The sprite track
The track name consists of a Node Path, followed by a colon, followed by a reference to its property, that we would like to modify.
In our example, the path is AnimationPlayer/Sprite and the property is position.
The path always starts at the AnimationPlayer node鈥檚 parent (so paths always have to include the AnimationPlayer node itself).
This still talks about 3.0.6, and the graphic also shows 3.0.6 AnimationPlayer
Thanks! I just made a PR to fix those issues.