Configuration structure header is created if the part is defined as configured in the Part screen. This is same for both purchased and manufactured type parts. 

But it seems the configuration flow (structure body) is not supported for purchased type and seems a limitation in the current design. Therefore, you will get this error.

Thanks for your answer Manoj, Actually the part is set as Configured on master part. I am just confused that if there is a limitation in the design, why the manual is reffering that it is possible to have purchase structure for conf. part. Do you know if there is any workaround?

Cheers

Yes, when you define the part as configured in master part, the configured structure header is automatically created for even purchase parts as structure type purchase but it seems the configuration flow (structure body) is not supported for purchased type even though the header is created. It seems a limitation. Therefore, I think the documentation is somewhat misleading.

Please check whether you can find any answer for a workaround from below 2 questions posted earlier.