I'm trying to draw an up or down arrow next to a chord. This is common notation in classical guitar for strum direction.
It seems that the most likely way to make this happen is to use \arpeggio and set the arpeggio stencil to draw a straight line. I saw https://lists.gnu.org/archive/html/lilypond-user/2019-12/msg00080.html that gives some hints about how to do stencils but maybe a more clear tutorial or set of examples would help.
Or, perhaps, there's a better way to do this. I am, of course, open to any suggestion.