\defineheadalternative
  [mine]
  [alternative=vertical,
   renderingsetup=minetoo,
   left=(,
   right=)]

\startsetups[minetoo]
    \headsetupspacing
    \ifconditional\headshownumber
        \headalternativeparameter{left}
        \headnumbercontent
        \headalternativeparameter{right}
    \fi
    \quad
    \headtextcontent
\stopsetups

\setuphead[section][alternative=mine]

\starttext

    \section{test}

\stoptext
