Binding key to bionics - where i goes wrong?

in my list of passive-bionics i have many bionics with binded keys which not needed. but in list of active bionics some bionics not have binding slot to keys and when i try to bind binded key - i fail. but i not see possibility to unbind key from bionics.

maybe i missed somewhere? i dig three times all menu of bionics - but can’t see nothing.
i see
! learn - delete (delete bionics or delete binded key? i think its deleting of bionics - am i right) = re-bind TAB - change type of bionics. and its all. nothing more.

how to unbind key from passive bionics?