Where to place menu for both book and doc?

Question

Dear all,
The script I'm developing creates a menu for the various steps to be taken by the user. It acts both on a single document or on a book (all of it's documents). Adding the custom menu to the SpecialMenu works fine for the documents. This standard menu is not available if a book is active. Hence I tried to connect it to the FormatMenu.
function DefineMenus() {
     var menuMain = {en: "Bibliography with EndNote …",
                    de: "Bibliografie mit EndNote …"};
     var menuDocu = {en: "Documentation",
                    de: "Beschreibung (en)"};
     var menuLocation = app.GetNamedMenu("FormatMenu");
     var bibenMenu  = menuLocation.DefineAndAddMenu("!BIBENmain", (localize(menuMain)));
     bibenMenu.DefineAndAddCommand(1,"BibenDocu",    (localize(menuDocu)), "");
I observe the following:
Invoke the script after FM has started and no book or document is open:
The menu is placed and available in an open document, but not in a book independently which is opened first.
Invoke the script after opening a document and then a book:
The menu is available in the document, but not in a book
Invoke the script after opening a book and then a document:
The menu is available in the document, but not in a book
What must be done that the menu is available for books and documents?

Answer 1

Thanks Jang - in the meantime I had a similar idea, noting that in the menu.cfg files there both a FormatMenu and a BookFormatMenu exists. But even this does not help:
     var menuLocation = app.GetNamedMenu("FormatMenu");
     var bibenMenu  = menuLocation.DefineAndAddMenu("!BIBENmain", (localize(menuMain)));
     bibenMenu.DefineAndAddCommand(1,"BibenDocu",    (localize(menuDocu)), "");
     menuLocation = app.GetNamedMenu("BookFormatMenu");
     var bkbibenMenu  = menuLocation.DefineAndAddMenu("!BIBENmain", (localize(menuMain)));
     bkbibenMenu.DefineAndAddCommand(1,"BibenDocu",    (localize(menuDocu)), "");
The effect is the same as before!
I'm invoking the script without using the ESTK (because this does not work for my custom-installation of FM). I write the script in EditPadPro, save it and invoke it via File > Scripts > Run (or the catalogue). So far I'm successful - atbeit somewhat slow - with my development.
This separtation process may require that I do the second part of the menu definition this way:
     menuLocation = app.GetNamedMenu("BookFormatMenu");
     var bkbibenMenu  = menuLocation.DefineAndAddMenu("!bkBIBENmain", (localize(menuMain)));
     bkbibenMenu.DefineAndAddCommand(1,"BibenDocu",    (localize(menuDocu)), "");
In this case the menu entry Format > Bibliography... is present in both the document and the book, but in the book it is gray (inactive). So there is still a missing link.
Ah, now I got it: also the submenu items must be different:
     var menuLocation = app.GetNamedMenu("FormatMenu");
     var bibenMenu  = menuLocation.DefineAndAddMenu("!BIBENmain", (localize(menuMain)));
     bibenMenu.DefineAndAddCommand(1,"BibenDocu",    (localize(menuDocu)), "");
     menuLocation = app.GetNamedMenu("BookFormatMenu");
     var bkbibenMenu  = menuLocation.DefineAndAddMenu("!bkBIBENmain", (localize(menuMain)));
     bkbibenMenu.DefineAndAddCommand(1,"bkBibenDocu",    (localize(menuDocu)), "");