Replace the 'armature layers' operator (which would toggle visibility of
armature layers) with the 'bone collections' menu (which allows assigning
to and unassigning from bone collections). The functionality of these
operators is quite different, but it unifies the behaviour between
armature pose and edit modes.
Selecting which bone collections are visible in the 3D Viewport may be
reintroduced after nestable bone collections are implemented. Otherwise
the list of bone collections will likely become unwieldy.
Sybren A. Stüvel
b48031df8e