SetOptions[
    EvaluationNotebook[],
    StyleDefinitions->Notebook[
        {
        Cell[StyleData[StyleDefinitions->"Default.nb"]],
        Cell[StyleData["Title"],MenuCommandKey->None],
        Cell[StyleData["Chapter"],MenuCommandKey->None]
        },
        WindowSize->{808,689},
        WindowMargins->{{38,Automatic},{-80,Automatic}},
        Visible->False,
        FrontEndVersion->"11.1 for Mac OS X x86 (32-bit, 64-bit Kernel) (January 4, 2017)",
        StyleDefinitions->"PrivateStylesheetFormatting.nb"
    ]
]

Item[KeyEvent["1", Modifiers -> {Option}], "Style" -> "Title"]

MenuSetup.tr > KeyEventTranslations.tr > Operating System