Thank you, Wolfgang,

that's exactly what I wanted.

Greetings
Thomas

Am 26.03.24 um 17:12 schrieb Wolfgang Schuster:
> When you use "header=high" you can't have a header because the block 
> for it no longer exists, compare the results for "header=high" and 
> "header=empty" in the following example.
>
> %%%% begin example
> \showframe
>
> \starttext
>
> \setuphead[chapter][header=high]
>
> \chapter{Lorem Ipsum}
>
> \dorecurse{10}{\samplefile{lorem}}
>
> \setuphead[chapter][header=empty]
>
> \chapter{Lorem Ipsum}
>
> \dorecurse{10}{\samplefile{lorem}}
>
> \stoptext
> %%%% end example
>
> As you have guessed \definetext is the way to create a custom header 
> for the first page of your \chapter, the command has like 
> \setupheadertexts a variable number of arguments.
>
> The third argument with the horizontal position can only be used when 
> you use two or four arguments to set texts on the left and right side 
> but isn't in my example because a) the text position is the default 
> and b) I pass only one argument for the content because I wan't the 
> text in the middle.
>
> %%%% begin example
> \showframe
>
> \definetext
>   [chapterheader] % identifier
>   [header]        % vertical position (header/footer)
> % [text]          % horizontal position (text/margin)
>   [This is a custom header for \tex{chapter}] % content
>
> \setuphead[chapter][header=chapterheader]
>
> \starttext
>
> \chapter{Lorem Ipsum}
>
> \dorecurse{10}{\samplefile{lorem}}
>
> \stoptext