Scaling animation in animation window issue/bug (Not displaying blue box)

Based on manual page above I am trying to rescale animation throug dopesheets, however when I select more keys no blue box appears and I am not able to scale them.

Did I miss some little icon or something ?

I am using Unity 5.1.1f1 (64-bit)

That scale feature was added to Unity in version release 5.5. IDK if it is being rolled back to previous versions.