> _("Idx") was translatable. I made a mistake and changed it to "Idx:" > and now it is translatable again: _("Idx: ").
This is not what I meant. "Idx: " is not translateable because it is not a word. The label should have the name "Index" not "Idx". This could then be translated to different languages, e.g to "Índice" when you use Spanish menus.
regards Uwe