I might need a little more help just to understand how best to adapt this to my situation:

One thing is clear: I was attempting to use a 'list' variable, and I can see why that was an error, since it is headertexts, not TOC that I want to influence.

But let me simplify my situation:

You seem to suggest initially that I could use \structureuservariable (or \structurevariable) instead, especially since I already have a variable to call on, e.g \startchapter[title={My title}][author={A. uthor}]. But in the example you then gave, you made no use of either of these.

My current setting is:

\setupheadertexts   [{\hfill\getmarking[chapter]\hfill}][]   [{\hfill\documentvariable{metadata:title}\hfill}][]

which gives me the book title centred on verso pages, and the chapter title centred on recto pages. All I want to do is to have the chapter contributors' name for each chapter instead of the chapter title.

So why can't I create a setups along the lines of:

\startsetups[contributor] \getmarking[\structureuservariable{author}] \stopsetups

Then just swap 'chapter' in \setupheadertexts, with 'contributor'? I tried it but it doesn't work. I thought it would be logical. Clearly I'm wrong but don't appreciate why.

Julian

The *list* variables work only in lists.

There’s also \structurevariable and \structureuservariable.

Make sure you use setups for the header, otherwise the variable gets expanded only once at the beginning.

Like in:

\setuppagenumbering[alternative=doublesided]
\setupheadertexts[] % empty
\setupheadertexts[\setups{text right}][][][\setups{text left}]

\startsetups[text right]
\rlap{\pagenumber}
\hfill
\getmarking[chapter]
\hfill
\llap{Un Nom}
\stopsetups

\startsetups[text left]
\rlap{Una Person}
\hfill
\getmarking[section]
\hfill
\llap{\pagenumber}
\stopsetups