I thought this should work, since \structurelistuservariable{author} 
works fine to call the author name into the TOC, but the same does not 
work for header texts it seems:

\setupheadertexts

[{\hfill\getmarking[\structurelistuservariable{author}]\hfill}][]

[{\hfill\documentvariable{metadata:title}\hfill}][]

But it doesn't. What am I doing wrong?

Julian