On 30 Jan 2018, at 17:37, Wolfgang Schuster <schuster.wolfgang@gmail.com> wrote:

[…]
Is there a way to make the \defineseparatedlist command to be more tolerant for the filename?

No but you can remove the space with Lua.

\externalfigure[\cldcontext{string.collapsespaces("\getvariable{talk}{picture}")}]

Thanks again! That does it.

However, it seems strange that the \externalfigure command does not accept a space in front of the file name nor after the file extension, while \input is very tolerant in that respect. Compare

\input knuth.tex

\input{knuth.tex}

which are all accepted, while when there is a space after the extension,

\startplacefigure[number=no]

\externalfigure[hacker.jpg ]

\stopplacefigure

or a space before the filename

\startplacefigure[number=no]

\externalfigure[ hacker.jpg]

\stopplacefigure

then ConTeXt does not recognize the file…

Maybe Hans has a reason to explain this behavior, but it is not clear to me.

Best regards: OK