I am happy that I can specify paginated print header/footer formatting overrides directly in the document metadata, ie.
Header Font: Times New Roman
However it would be optimal if my custom CSS could directly style the header and footer lines. Are there selectors which can be used for that, or could there be?
It would also be an improvement if there could be a Center definition:
Print Header Center: %title
Print Footer Center: %page
You could support this in per-document metadata even before you figured out a way to squeeze it into the Settings / Export Pane UI!