Can anyone help me with a menu question…

I have been attempting, without much success, to add a menu option to a package (sublime-jslint) which toggles a feature each time the menu is selected. As the documentation (hah!) suggests, I have looked through the existing Main.sublime-menu files to find an example to copy. The closest I can find is in …/Default/Main.sublime-menu, the snippet is:

{ “command”: “toggle_save_all_on_build”, “caption”: “Save All on Build”, “mnemonic”: “A”, “checkbox”: true },

I am guessing that ‘toggle_’ is a prefix that specifies ‘save_all_on_build’ is a boolean defined somewhere - but where? And, what is the significance of ‘mnemonic’ ?

–
Andy