The circuit currently being editted will be saved in a file under a different name when this menu item is selected. A file chooser dialog will pop up in which you can specifiy the new name of the file. The circuit name in the editor will be changed to reflect the new name.
The new circuit name must consist of letters, digits and underscore, and it must begin with a letter.
Putting the .jls extension on the name in the file chooser dialog is optional. If you don't, JLS will add it for you.