> But now I have a figure, where the (pretty long)
> title-text should be on the right side, how to
> get this?

Define a float type `rightfigure` that inherits from `figure`;
then setup that float's caption with \setupcaption[rightfigure][...=...].
Like so:

\definefloat[rightfigure][rightfigure][figure]
\setupcaption[rightfigure][location=right]

\starttext
\placefigure{caption 1}{\framed{figure 1}}
\placerightfigure{caption 2}{\framed{figure 2}}
\placefigure{caption 3}{\framed{figure 3}}
\stoptext

Example stolen from:
http://wiki.contextgarden.net/Command/setupcaption
On what wiki pages did you look? Perhaps you could add a sentence
'For adjusting the captions and their location, see {{cmd|setupcaption}}.'
so that future users will be led to the page they need.

Cheers,
Sietse