Can Visio do Sankey? While there are no Sankey Diagrams templates that ship with Visio, there are a few in-the-box shapes that can be used to create rudimentary Sankeys.
He identifies some problems with the Visio-supplied arrow shapes, and provides “a new version of the arrow shape which is more suitable to making Sankey diagram” for download. Really cool, Visio Guy!
In one of the follow-up comments Chris states that pre-built shapes can only cater for the most basic Sankey arrows, but “a proper, full-blown solution would utilize at least some code, if nothing else, for decent data-input dialogs, etc.”