Have the possibility to modify a mock while it has not been called by anyone

[SBrendan]

Hello !

I would like to add a new feature allowing to modify a mock, while it has not been called by one of the services. Today it is impossible to do this and in case of error in creating a mock you have to reset the session or add a more precise mock to override the old one. If the mock has already been called, I understand that it cannot be modified. But if this one has never been called I think that it is not a problem to edit it

Thank you :)