Hello Bille,
Do the following steps and you will get the required graph:
1) Select the report page.
2) Drag and drop a 2D graph into the report.
3) From the Project Browser, select the Fiber Length and drag and drop the parameter X shift into the X-axis of the graph.
4) From the Project Browser, select the BER Analyzer and drag and drop the result BER into the Y-axis of the graph.
Good luck.
Cheers,
Ahmad