> BTW: is it possible to define the footnotes somewhere else?

You mean like \useurl and \url?

Yes, it now 'distracts' from the main info.

No, what’s possible is this:

\startbuffer[footnote:a]

Note A

\stopbuffer

\startsetups[footnote:b]

Note B

\stopsetups

%\setvariables[footnote][c={Note C}]

\setvariable{footnote}{c}{Note C}

\starttext

A\footnote{\getbuffer[footnote:a]}

B\footnote{\texsetup{footnote:b}}

C\footnote{\getvariable{footnote}{c}}

\stoptext

You can write a feature request because it’s easy to add this functionality but it depends on Hans.