\defineindenting[whatever][yes,2cm]
%defineindenting[whatever][yes,-2cm]

\starttext

\startbuffer
    \setupindenting[yes,-2em] \input ward \par
    \setupindenting[yes,2em]  \input ward \par
    \setupindenting[whatever] \input ward \par
\stopbuffer

\getbuffer

\defineindenting[whatever][yes,-2cm]

\blank

\getbuffer

\stoptext
