Hi!

I am trying to create a custom reference line with the letter module.
I would like for instance to display the typical phone and email fields
and additionaly eg a not yet existing field such as mobile={12345} (or
foo={bar})

At first I did not manage to have any field displayed at all but the use
of setupletterlayer as described in
https://mailman.ntg.nl/pipermail/ntg-context/2013/073560.html helped
(seems the manual from 2010 is no longer up to date...). Unfortunately
this writes the reference line with labels only for phone an email but
not for mobile nor foo, The value of the parameter is writen though, so
it seems I am half the way.