On 2013–09–10 R. Ermers wrote:

> I have problems with the placement of floats. I need them to be
> placed in the outer edge of the text, but Context puts them in the
> middle of the page. The outer, inner, outeredge, inneredge,
> commands do not work. Right and left do work.

You probably confused edge and margin. By default the edge has zero
width and has to be enabled using \setuplayout.

> Preferably the criterium option should also work

\setupexternalfigures
  [location=default]

\setuppagenumbering
  [alternative=doublesided]

\definefloat
  [marginfigure]
  [marginfigures]
  [figure]

\setupfloat
  [marginfigure]
  [default=margin,
   criterium=\marginwidth]

\setupcaption
  [marginfigure]
  [number=no]

\showframe
\starttext
  \dorecurse{9}{%%
    \input knuth
    \startplacemarginfigure
      \externalfigure [cow] [width=\recurselevel cm]
    \stopplacemarginfigure}
\stoptext

Marco