Another option is to use the Install custom menu script to selectively install custom menus for each layout. This way, you can have a custom menu set with the value added options and a second menu set that does not list the value added options.
Note that menu item names can be the result of a calculation if you click the specify button. It'd be nice if the calculation allowed you to apply font styles or colors. I haven't tried that, but you can experiment to see if any such function works as there is a textcolor and also a fontstyle function defined in FileMaker. At the very least, such a calculation might be able to append "--Not Available" or some such text to the name of the menu option and it can be set to run a "do nothing" script so that nothing happens when the user selects the option. (Might be a nice way to advertise the value added modules if the user sees what he doesn't have...)
At the very least, such a calculation might be able to append "--Not Available" or some such text to the name of the menu option
Turns out this suggestion led me to the exact results I was looking for! Instead of using a calculation to return alternate or appended text for the menu item, I'm using it to return no text. In my case I'm using submenus and using the calculation to return no text (i.e. the empty string ""). When the condition isn't met, it results in the parent menu item dimming out, exactly what I was looking to do in the first place. Screenshot illustrating both scenarios is attached. Thanks!
Cool! Saving this info for future use....