We recently upgraded to latest 11 version.
We were happy to see the new feature of adding column.
But after adding column we wish to save it.
But when try to save it with different name than it shows error stating this report should be in custom format
This doc outlines three means to create your own reports: Report Builder, Query or Script.
To customize a standard default report is yet another option. In which case this may help you Report customization (Any report)
To post your error traceback would help resolve your problem context too thanks!