> I have something that kind of works, based on some LSR snippets,
> but it moves the chord symbols above marks, rather than below.
> Does anyone have any suggestions for keeping the chord symbols in the
> same location as normal?
The ChordNames context definition in engraver-init.ly has the line
> \consists "Axis_group_engraver"
If you add this to your definition, the placement is restored.