Locking sankey nodes for sharepoint purpose

Hi,123abc ,thanks for your concern about this issue.
And I would like to share some additional solutions below.
Hello,Anonymous .I am glad to help you.
This is my test:

After my testing, there seems to be no direct way to disable the user from moving the nodes in the graph (this is an interactive behavior)
Maybe you could try setting the visual that you don't want the user to move to a static image (which would result in a loss of interactivity)
Understanding your concern, you can set up the following functionality in for reports:
When each user views a report, the report's presentation state is always maintained as the report's published state, and user-made changes such as node moves are cleared. The default state of the report is the same for all users opening the report.

Tick "Don't allow end user to save filters on this file in the Power Bi service.

Solved: clear filters when you return to BI page - Microsoft Fabric Community

I hope my suggestions give you good ideas, if you have any more questions, please clarify in a follow-up reply.
Best Regards,
Carson Jian,
If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.