\setupalign    [r2l]
\setuppapersize[A4][A2,landscape]
\setuplayout   [location=middle]

\showframe

\starttext
    \inmargin{Margin}text\par
    \inleft    {Left}text\par
    \inright  {Right}text\par

    \inmargin{Margin}\par text\par
    \inleft    {Left}\par text\par
    \inright  {Right}\par text\par
\stoptext
