Not really a bug 'per se' more of a performance tweak
The fade in / fade out animation of the popover for entering a new language key is too long. When entering many language keys it get's quite tedious having to sit there waiting for the animation to catch up. Plus if you hit the add new key button too quickly the new dialog appears only to fade out again.
I personally would either make the animation very short, or get rid of the animation altogether.
It would also be good to have a way of entering multiple language keys.
/DM