When you wish to bake your NLA animation mix into one Action,
The Bake option in the Animation tab will not work.
The way to do this is to:
- Select the object in Object Mode.
- Press Space and type ‘bake‘
- Choose Nla: Bake Action
- In the Bake dialog, select Pose, deselect Only Selected, and press OK.
- After the process, the Armature will have a new action that is the baked animation.