Can't create Keyframes

Godot Version

4.3 Stable mono

Question

Why can’t i create Keyframes for my rotation animation?

I have a Sphere MeshInstance3D. As a Child there is an AnimationPlayer within I have a property track for my object with a rotation vector node. When I want to create a Keyframe for this Animation nothing happens exept a blank inspector for an AnimationTrackKeyEdit pops up.

I figured that it might be a but with the Snap Option but i am not sure. Snap is on and set to 50. Animation length is 1000.
This is supposed to be a Star to slowly rotate around itselfe.

Can you show code how you make keyframes?