Hello Otared,

thanks for the hint. However, I'm still not able to tune the numbering setup fully.

Now I have (with resulting numbers | desired number):

----
\setuphead[part,chapter][placehead=yes,page=no]

\setupformulas
[prefix=yes,
   %prefix=no,
   %prefixsegments=chapter:section,
   prefixsegments=part,
   way=bysection,