It took me quite a while to find the solution for this problem. By posting it here, I hope this will be useful to others.
\completecontent set the list composed of the chapters with a previous call to:
\setupcombinedlist[content][list=chapter]
and the list of chapters and included sections with:
\setupcombinedlist[list={chapter,section}]
etcetera.
Hans van der Meer
I am very sorry, but I still cannot understand how to get the TOC as I would like it.
The following does typeset the Content header but is empty otherwise.
\startfrontmatter
\completelist[content][criterium=chapter]
\stopfrontmatter
I tried various possibilities from the reference manual, like \placelist[section][criterium=chapter]. But either this doesn't work (anymore?) or I am doing something very stupid. But these call do nothing.
It seems so simple: use the \complete.. mechanism (because this wraps the TOC nicely) to typeset a selection from the TOC using the criterium-mechanism. Which seems to me just made for this sort of action. But nothing comes out of it.
Hans van der Meer