The optional columns for tooltip and style won't help you to implement the kind of sankey diagram shown in the image.
I don't know of any general chart API that can do all this, and I suspect such charts are drawn with special purpose code that can only draw the one chart in question. Assuming it is possible, several additional code changes to the sankey chart will be required to support the new features required (i.e. arrowhead connectors, custom connector labels, node orientation angle, invisible nodes, frameless nodes, custom node contents), but it will be a while before we can get to it.