Found this very simple online Sankey diagram drawing application developed by Jan Stępień. It is a very very basic interface where you can define nodes (“Processes”) and streams (“Reagents”) between source and sink nodes. The whole thing is in black and white and you will get outputs like these:
I played around a bit with the tool, but didn’t quite manage to do my own Sankey diagram. See for yourself. The code is open source, so if anyone wants to contribute… I updated my software list.