I'll second that one :)
I think the reset puzzle button should also be on the undo window. I rarely use anything except this window so it is annoying to have to switch to reset.
Where would you want to put the Undo window instead? Maybe there's a way to accomplish what you're looking for without writing a lot of extra code to implement docking.
skyleriberg, what if the reset puzzle button were next to the puzzle name, on the score display window? Would that work as well for you?
was more along the lines of an undockable, resizeable window.
That way any given user can choose where to locate the undo window and how large the content would be