Dear List,
I just finished my example, did some changes today and it works perfect
\setuppapersize[A8,landscape]
\setuplayout[leftmargin=2.5cm,
             leftmargindistance=0.2cm,
             backspace=2.9cm,
             width=4cm]
\margintext{\blackrule[color=black, height=0.05ex, width=1cm]\\}\blackrule[color=black, height=0.05ex, width=4cm]
\starttext
\margintext{2.1.1}\
{Ach ist das schön, dass du da bist.}
\stoptext

Uschi