I've the same problem just like this.https://support.soxware.com/communities/1/topics/1245-unable-to-select-bones-in-scene-view
When the bone is parented inside collider it will not selectable. But only when the collider is in custom layer.
I tried this with my projects. And I found that when I parent my character bones inside a character controller if the character controller is set at "Default" layer everything work fine. but when I change the character controller to my "Player" layer. I cannot select any bones inside. Because Unity Character Controller come with default capsule collider. I also tried this with the box collider and it produces same result.
Now my solution is to disable the Character Controller (collider) before animating in Umotion or another way is to create a separate mesh and armature for animating.
I think it would be more convenient if we can animate any armature inside the character controller.
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