> 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
\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