Although the strings that are displayed in the menus appear to be explicitly listed in the defining code, such as SCPluginUIDaemon/SCUIDaemonController.m, this is not strictly so. Actually, the strings found here are used to look up the true strings in the file SCPluginUIDaemon/Resources/English.lproj/menuitems.strings (or some other language instead of English).
Now, I admit that if a string in the code isn't found in the menuitems.strings file, the run-time system will just quietly use the code string. But we don't want to do it that way, because one important use of the menuitems.strings file is for translating menu labels into other languages. To do that, yo ujust ahve to create a parallel directory in the Resources folder, and translate the strings.
Even for English installations, though, one kind of menu item requires the menuitems.strings file trick: commands that require some sort of dialog before they actually do any work are required, by the Apple UI Guide, to have lavels that end in the ellipsis, "…". This is not the same as three periods! It's a separate character (which you can type by holding "option" and pressing ";", at least on English keyboards you can). You can't enter this character directly into source code, but you can enter it directly into the menuitems.strings file. There are several examples there for you to examine.
So: enter your menu pick code in SCPluginUIDaemon/SCUIDaemonController.m in the obvious way (without ellipses), and then make an entry in menuitems.strings as well.