I don’t think mock servers support matching by request body yet, you can open a feature request in the issue tracker on github for the same.
Meanwhile, you could use custom headers like x-mock-response-name and x-mock-response-id for matching. It is explained in a little more detail in this answer.
Feel free to ping here in case you need some help in setting this up and I or someone else from the community would be happy to help. 