There are points in the design process I'd like to have saved so that I can go forward and experiment knowing that I can easily returned to a desirable state if things go awry.
I know this is somewhat a time line issue, but I don't always want to scroll backwards and determine exactly where I need to be. Using command-z is tiresome as well if one wants to go back more than a couple steps.
Why can't we have an option of saving a particular stage/state of the model that can be returned to with a few clicks.?