How do I enable the Flip Active/Selected Bones options? Flip Active/Selected Bones with Armature in Pose Mode.
Currently the options are disabled. The goal is to get them enabled and functional.  The options respond to hover movements but mouse click has no effect in the panel UI or the 3D View window.



Click Image for larger view. Composed image. OS is Windows 10.

How do I get the options enabled?


Active Only 
Extend


If I run the following script from the text editor window it is successful.



In related contrast,  the similar feature does works fully with options in 

[Edit Mode].

[Edit Mode] successful.  [Pose Mode] not successful.

Its slightly interesting that the menu names are different in pose mode and edit mode.  The panel titles are the same.



link
https://www.blender.org/api/blender_python_api_2_69_4/bpy.ops.pose.html


  bpy.ops.pose.select_mirror(only_active=False, extend=False)
  
  Mirror the bone selection
  
  Parameters:   
  
  
  only_active (boolean, (optional)) – Active Only, Only operate on the active bone
  extend (boolean, (optional)) – Extend, Extend the selection
  


Thanks.
The operator properties are disabled when global undo is disabled



As for the menu variations, that would be to reflect the way the operator performs. Most of the select_mirror operators change the selection to be items on the opposite side, this can even lead to no active vertex in the selection. But the pose mode select_mirror operator will select the mirrored bone unless both bones are already selected when it will only change the active bone and not alter the selection.