Markup in ChordNames context

[Peter Chubb]

Hi,
        Sometimes in vocal+ukulele music I want to indicate that a
        particular chord uses an alternate fingering.  I'd like to add
        an asterisk and a footnote with fret diagram for these cases.
        But the obvious
            \chordmode { d^"*" }
        fails with  "error: string outside of text script or
        \lyricmode"

        I'm using Lilypond 2.22.2

        Can someone give me a clue?

Peter C