You can delete objects on the stage with the delete key...
but is there a way to add new objects on the stage?
I was working with the AS2 version - I am not familiar with AS3 yet.
I tried to attach a new movieclip with a button but it messes it up:
on(click){
var a:MovieClip = _root.attachMovie("pic_mc", "test_mc", this.getNextHighestDepth(), {_x:25, _y:25});
}