Bone Collections group the bones of an Armature into named collections. The armature is the owner of these collections, so they are available in all modes. Bone Collections are identified by their name, which are unique within the Armature.
In the text below, “collection” is understood to refer to “bone collection”; Scene Collections are not described here.
Bone Collections can be managed via the Armature and Bone property panels.
Bone Collections can be shown & hidden via the list in the Armature properties, as well as via the list in the Bone properties. Bone visibility is determined by the visibility of its collections, and its own ‘hidden’ property:
If the bone itself is marked as ‘hidden’, it is invisible regardless of the bone collections.
A bone is visible when it is contained in any visible collection.
A bone that is not assigned to any bone collection is visible; otherwise it would be impossible to select it & assign it to a collection.
Bone collections can be added using library overrides. For this to work, both the armature Object and the Armature itself need to be overridden.
There are a few limitations when it comes to bone collections & overrides:
Only bone collections that are local to the current blend file can be edited.
Bone collections that already existed on the linked-in Armature are read-only, and only their visibility can be toggled. Those visibility changes won’t be saved, though.
Custom properties of overridden bone collections cannot be edited in the properties panel. Python access is fine; this is just a current limitation of Blender’s UI code.
How It Works
Bone collections added via overrides are ‘anchored’ to the preceding collection, by name. Here is an example. The italic collections are defined on the linked Armature in armature.blend. The bold ones are added by overrides in armature_shot_47.blend.
Left Pinky (anchored to “IK Controls”)
Right Pinky (anchored to “Left Pinky”)
Now if the Armature in armature.blend gets updated with two more collections it might look like this:
Face Detail Controls
After reloading armature_shot_47.blend, it will look like this:
Left Pinky (still anchored to “IK Controls”)
Right Pinky (still anchored to “Left Pinky”)
Face Detail Controls
Bone Collections were introduced in Blender 4.0, as a replacement for armature layers and bone groups. Bone Collections are owned by the Armature, so they are available in all modes. To contrast, bone groups were stored on the object’s pose, and thus were not available in armature edit mode.