undo and redo

how do u do that in this software?? contrl z and control y don't seem to wrk..and also in the tool bar there is no undo and redo under EDIT
thnks

 

Ctrl Z Ctrl Z

As far as I can tell...there isn't an 'undo' facility...unless anyone else has found it?
It would be particularly useful to be able to bring back wrongly deleted parent clips with at least a one level undo.