I think it would be a great addition, if you could lock elements such as the header or footer to the top or bottom for instance. The way this could work is that you could label/define these elements as locked and then in the viewer mode they would stay at this position while scrolling (up or down). This would be useful for a better and more realistic feel of the final application or website (in case that function was considered). Something similar can be found in a tutorial of the pixate application explaining their scroll function. (http://www.pixate.com/education/video-tutorials/scroll-animations/)
I do really need this feature. Especially, in my current project it comes hard to me to explain the intended scroll pattern. I would appreciate just showing the behavior instead of "Now figure out the nav would stick... and...".
Are there any current plans to that feature?
You also have my vote for implementing scrolling in presentation mode :)
And within this feature, defining which area is scrollable –the rest would be fix.
I cannot user test how easy to find is an element if my prototype forces me to show all elements or work with collapsible elements :)