\environment math-fonts-helpers

\startbuffer[accents]
    $+\bar{u}\bar{f}\bar{\Omega}$
    $\overbar{u}\overbar{f}\overbar{\Omega}$
    $\overline{u}\overline{f}\overline{\Omega}$
    \blank
    $\dot{u}\dot{f}\dot{\Omega}$
    $\hat{u}\hat{f}\hat{\Omega}$
    $\tilde{u}\tilde{f}\tilde{\Omega}$
    \blank
    $\ddot{u}\ddot{f}\ddot{\Omega}$
    $\widehat{u}\widehat{f}\widehat{\Omega}$
    $\widetilde{u}\widetilde{f}\widetilde{\Omega}$
\stopbuffer

\starttext
    \MathSamples [
    ] [
        accents
    ]

\stoptext