% only works in new loader

\startluacode
    fonts.handlers.otf.addfeature {
        name = "ptest",
        type = "pair",
        data = {
         -- [0x0153] = { [0x0301] = { { 0, 0, 0, 0 }, { -500, 0, 0, 0 } } },
            [0x0153] = { [0x0301] = { false,  { -500, 0, 0, 0 } } },
        }
    }
\stopluacode

\definefontfeature[default][default][ptest=yes]

\setupbodyfont[cambria]

\starttext

    \unexpanded\def\oeacute{\char"153\char"301\relax}

    b\oeacute f

\stoptext
