I have done things like this in the past:
\version "2.23.81"
\language "english"
seven-eighths-sharp-markup = \markup
\combine
\musicglyph #"accidentals.sharp.slashslash.stemstemstem"
\path #0.15
#'(
(moveto 1.25 1.15)
(lineto 1.25 2.0)
(moveto 0.95 1.2)
(lineto 1.25 2.0)
(lineto 1.55 1.2)
)
\score {
\new Score <<
\new Staff {
c'4
cs'4
\tweak Accidental.stencil #ly:text-interface::print
\tweak Accidental.text \seven-eighths-sharp-markup
cs'!4
}
>>
}
You may want to adjust the appearance of the arrow yourself. And because this arrow does not match what is in the font, I have a little library of such markups here for example: https://github.com/GregoryREvans/abjad-ext-microtones/blob/master/abjadext/microtones/lilypond/general-edo-accidental-markups.ily
regards,
gregory evans
p.s. the limitation of this method is that the accidental must already be visible for the tweak to appear, so either it needs to be set to "dodecaphonic" or use the "!" like in my example.