Hi,
Let me clarify my question more...
I need to attach some value to a chapter in that key. That custom prefix + the value in the key is ment to be in the header or a footer as a matter of fact. The case can apply to both headers and footers.
I tried:
\chapter[title={A sample title}][custom_random={custom_value}]
\setupheadertexts[{Prefix: \structureuservariable{custom_random}}]
...
\stopchapter
I tried this code when trying to figure out the mechanism. The prefix string in placed in the header, but hte custom value of the attached key is not expanded..
Evey page will contain just one section started by a \startchapter and \stop chapter. I would like to put this custom attached value in the right slot in the document header.

I hope that htis time around htigs are more clear.

On Tue, Dec 20, 2022 at 8:13 PM Henning Hraban Ramm via ntg-context <ntg-context@ntg.nl> wrote:
Am 20.12.22 um 19:44 schrieb Pawel Urbanski via ntg-context:
> Dear Friends,
> I spent some time searching and coding simple documents, but failed and
> therefore I'm asking for help...
> A section such as chapter cn have custom keys with values. One uses the:
> \structureuservariable command to access such values.
> How can I use such a value to create a custom header in a format:
> Prefix: \structureuservariable{foo}
>
> I am asking for the only thing that worked when I tried was calling the:
> \setupheadertexts command inside a chapter environment block with some
> prefix. Unfortunately the value from the custom field was not expanded.
> It was correctly inserted in a regular paragraph.
> For example:
> \startchapter
> [title={A sample title}][custom_something={random_value}]
> ...
> \stopchapter
>
> How can I put the value of: custom_something in the header with some prefix?

\define[2]\MyChapter{No.#1 – Prefix
\structureuservariable{custom_something}: #2}

\setuphead[chapter][
  command=\MyChapter,
]

Is this what you meant?

Hraban
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