You can write a new workspace - but it accepts an existing name!
I constructed a workspace and saved it as GJ DEFAULT. Later I modified it and saved it under the same name. At worst, I thought it would refuse, at best it would ask me if I wanted to overwrite the existing one. It did neither and I ended up with two workspaces with the same name. How odd.
(sigh...) I know - this was raised as an issue a while back. It's
extremely confusing...