Hello Peter, thanks for your answer.

Unfortunately, I guess that it doesn't applied to my case as in SpaceClaim you don't have this "use as input parameter" check box. It seems that, once you create the parameter in the "groups" tab, you cannot undo that action. I mean, you can delete it or even ctrl+z it, but it will be already transfered to the workbench list, from which you won't be able to remove anymore. I don't know if I am missing something though.

Any other thoughts?