\def\Dedent{\begingroup\obeylines\obeyspaces\doDedent}
\def\doDedent#1{\directlua{
thirddata.dedent(\!!bs\normalunexpanded{#1}\!!es, 4)}
\endgroup}
\protect
\dostartDedentA}
\def\dostartDedentA#1\stopDedentA
{\ctxlua{thirddata.dedent(\!!bs\normalunexpanded{#1}\!!es, 5)}%
\endgroup}
\protect