\setupheadertexts[chapter]

\define[2]\ChapterCommand
  {\vbox\bgroup\starttabulate
   \NC Title   \EQ \structurevariable{titledata.title}   \NC\NR
   \NC Marking \EQ \structurevariable{titledata.marking} \NC\NR
   \stoptabulate\egroup}

\setuphead[chapter][command=\ChapterCommand]

\starttext

\startchapter[title={Hello World},marking={Goodbye continent}][mybla=whatever]

\starttabulate
\NC Title    \EQ \namedstructurevariable{chapter}{title}   \NC\NR
\NC Title    \EQ \namedstructurevariable{chapter}{titledata.title}   \NC\NR
\NC Marking  \EQ \namedstructurevariable{chapter}{titledata.marking} \NC\NR
\NC Whatever \EQ \namedstructurevariable{chapter}{userdata.mybla} \NC\NR
\stoptabulate

\stopchapter

\stoptext

