3D skeleton -> How to create new bones?

Godot Version

4.3

Question

I am trying to create a custom skeleton3D in Godot from imported meshes. Problem is that I cannot figure out how to add bones to a Skeleton3D node. Every tutorial and guide I have seen imports a finished thing from Blender but they never create new bones in Godot. There are a few bone nodes but they all seem to have specific uses and don’t just create a new bone that can be animated.

Am I missing something?