Is it possible to add ..

ehm, if you really badly want it and if youre a little handy writing ActiveX DLL's in visual basic and API programming, have a look at this code:

Public Declare Function GetParent Lib "user32" (ByVal hWnd As Long) As Long
Public Declare Function GetMenu Lib "user32" (ByVal hWnd&) As Long
Public Declare Function InsertMenu Lib "user32" Alias "InsertMenuA" (ByVal hMenu&, ByVal nPosition&, ByVal wFlags&, ByVal wIDNewItem&, ByVal lpNewItem$) As Long
Public Declare Function GetActiveWindow Lib "user32" () As Long
Public Declare Function AppendMenu& Lib "user32" Alias "AppendMenuA" (ByVal hMenu&, ByVal wFlags&, ByVal wIDNewItem&, ByVal lpNewItem$)
Public Declare Function CreatePopupMenu Lib "user32" () As Long
Public Declare Function DrawMenuBar Lib "user32" (ByVal hWnd&) As Long
Public Declare Function GetFocus Lib "user32" () As Long
Public Declare Function GetForegroundWindow Lib "user32" () As Long

ublic Const MF_BYCOMMAND& = &H0&
Public Const MF_BYPOSITION& = &H400&
Public Const MF_POPUP& = &H10&
Public Const MF_STRING& = &H0&
Public Const MF_CHECKED = &H8&
Public Const MF_DISABLED = &H2&
Public Const MF_MENUBARBREAK = &H20&
Public Const MF_MENUBREAK = &H40&
Public Const MF_SEPARATOR = &H800&

Public Sub CreateNavMenu(ByVal Name As String, ByVal SubItems As String)
    ' get parent form hwnd
    Dim hWnd As Long
    Dim oldhwnd As Long
    hWnd = GetForegroundWindow
    While hWnd <> 0
        oldhwnd = hWnd
        hWnd = GetParent(hWnd)
    Wend
    hWnd = oldhwnd
    
    ' set menu
    Dim hMenu As Long
    Dim appHMen As Long
    hMenu = CreatePopupMenu()
    
    Dim myitems() As String
    myitems = Split(SubItems, ",")
    Dim i As Integer
    For i = 0 To UBound(myitems)
        If myitems(i) <> "-" Then
            AppendMenu hMenu, MF_STRING, i, myitems(i)
        Else
            AppendMenu hMenu, MF_SEPARATOR, 0, "-"     'If you want to add saperator then unComment this line
        End If
    Next i
    
    appHMen = GetMenu(hWnd)
    InsertMenu appHMen, 5, MF_BYPOSITION Or MF_POPUP, hMenu, Name
    DrawMenuBar appHMen     'Draw Menu bar to visible menu
End Sub

And this code only appends the menu, to know if the user clicked it you will need to subclass the menu. Then you can raise an trigger in C/AL and have C/AL code executed.

But, it all is a bit tricky and also keep in mind that Navision refreshes its menu regulary so your menu will disappear then. When navision refreshes its menu you need to refresh yours as well ..

Oh, and you asked how you could add a menu to an existing. This is also possible but don't have a code example ready but with this code youre close ..

Good luck