I am seeing buttons and links that say "Undo" in the portfolio tool UX work.
I am not sure if it is simply a mislabeled "cancel" button or if it is actually supposed to reverse changes.
As it stands, if I make a change to a portfolio name, description or choose some folks to share a portfolio with, I am presented with "Save" and "Undo" choices. If I "save" a change and then "undo", nothing changes (ie: there isn't a history log being maintained here). If I just "undo", it seems to not accept my changes (just like I would expect a "cancel" button might do).