I have mentioned this in a Tech Support track as well, but it serves as a warning here.
Using the style sheet editor, I associated a pre-existing style sheet with E.G. The path was incorrect for the server because it used a drive allocation, so I deleted the style sheet reference. I discovered that unfortunately this also deletes the physical file and I had to copy it back from elsewhere.
Since "deleting" a data set from the Process flow only removes the reference to the table, I expected the same behaviour in the style manager.