1. Create a union between the same tables.
2. Create a calculated field to create the endpoints of the Sankey chart
3. Create Bins, and freeze bin size to 1.
4. Calculate another calculated field to find percent to the total.
5. Now duplicate the above field and rename the field.
6. Create another field to show evenly spaced marks on the visualization.
7. Create a sigmoid function to get the curves.
8. Add the above fields in the sheet to get the final chart.
View this video for a complete explanation on how to create Sankey chart,
Hope it helps you.