Additional detailed specifications are listed here.
The virtual bone hierarchy data of Close Bone Picker is entirely stored in the Armature object's custom property "cbp_structure".
Each Armature can have its own separate hierarchy structure, and you can delete the registered hierarchy by removing this custom property.
When you register a hierarchy structure with multiple branches, CBP remembers the root of the previously selected branch. If you select the right hand, navigate back to the torso with Pick Parent, then use Pick Child, it will enter the right hand's root. If you select the head and navigate back, it will head toward the head's root next time.
The current specification does not allow registering multiple separate structures simultaneously. The registered hierarchy structure must be connected somewhere.
✗ Multiple separate structures cannot be registered
✓ A single connected structure can be registered