Thanks to this project: https://www.python-graph-gallery.com/
It's easy to create all kinds of charts and diagrams with Python, including Sankey Diagram.
However, I made some improvements to it. With an extra Excel file, it's now possible to set diagram data in two well organized spread sheets, one for nodes and the other for links, rather than doing it in the tricky json way. Save each sheet as an .csv file, then the code reads data from them and inserts it to the json structure.
Just download whatever in the assets folder and play with is locally.
See online demo here: https://colab.research.google.com/drive/15WgiAluGPgrnvp9I4QbBVMuy6bA7vbtR?usp=sharing