textwidth for what and why, you're in the right edge

> It could be textcommand. If so what does \command#1 mean ( see main
> manual pg 150 ) ?

\define[1]\SectionList
 {\framed{#1}}

\setuplist[section][textcommand=\SectionList]

\starttext
\placelist[section]
\section{Section}
\stoptext