%% http://lilypond.1069038.n5.nabble.com/Nice-workaround-for-simultaneous-rehearsal-marks-thanks-Neil-td3086.html

\version "2.21.2"

#(define (multi-mark-engraver ctx)
  (let ((texts '())
        (final-texts '())
        (events '()))

   `((start-translation-timestep
      . ,(lambda (trans)
          (set! final-texts '())))

     (listeners
      (mark-event
       . ,(lambda (trans ev)
           (set! events (cons ev events)))))

     (acknowledgers
      (break-alignment-interface
       . ,(lambda (trans grob source)
           (for-each (lambda (mark)
                      (set! (ly:grob-parent mark X) grob))
            texts))))

     (process-music
      . ,(lambda (trans)
          (for-each
           (lambda (ev)
            (let* ((mark-grob
                    (ly:engraver-make-grob trans 'RehearsalMark ev))
                   (label (ly:event-property ev 'label))
                   (formatter (ly:context-property ctx 'markFormatter)))

             (if (and (procedure? formatter)
                  (not (markup? label)))
              (begin
               (if (not (number? label))
                (set! label
                 (ly:context-property ctx 'rehearsalMark)))

               (if (and (integer? label)
                    (exact? label))
                (set! (ly:context-property ctx 'rehearsalMark)
                 (1+ label)))

               (if (number? label)
                (set! label (apply formatter (list label ctx)))
                (ly:warning "rehearsalMark must have
integer value"))))

             (if (markup? label)
              (begin
               (set! (ly:grob-property mark-grob 'text) label)
               (let ((dir (ly:event-property ev 'direction)))
                (and (ly:dir? dir)
                 (set! (ly:grob-property mark-grob 'direction)
                  dir))))
              (ly:warning "mark label must be a markup object"))

             (set! texts (cons mark-grob texts))))
           (reverse events))))

     (stop-translation-timestep
      . ,(lambda (trans)
          (if (pair? texts)
           (let ((staves (ly:context-property ctx 'stavesFound))
                 (priority-index 0))
            (for-each (lambda (grob)
                       (let ((my-priority (ly:grob-property
                                           grob 'outside-staff-priority 1500)))
                        (for-each (lambda (stave)

                                   (ly:pointer-group-interface::add-grob grob 'side-support-elements
                                    stave))
                         staves)
                        (set! (ly:grob-property grob
                               'outside-staff-priority) (+ my-priority priority-index))
                        (set! priority-index (1+ priority-index))
                        (set! final-texts (cons grob final-texts))))
             (reverse texts))
            (set! texts '())
            (set! events '())))))

     (finalize
      . ,(lambda (trans)
          (and (pair? final-texts)
           (for-each (lambda (grob)
                      (set! (ly:grob-property grob 'break-visibility)
                       end-of-line-visible))
            final-texts)))))))

\layout {
  \context {
    \Score
    \remove Mark_engraver
    \consists #multi-mark-engraver
    \consists Tweak_engraver
  }
}

markDown =
#(define-music-function (text) (markup?)
  (make-music 'MarkEvent
   'direction DOWN
   'label text))

myMark =
#(define-music-function (text) (markup?)
  (make-music 'MarkEvent
   'label text))

toCoda = {
  \tweak self-alignment-X #RIGHT
  \tweak break-visibility #begin-of-line-invisible
  \myMark \markup { "to" \hspace #1.25 \raise #1.25 \musicglyph "scripts.coda" }
}

DSalCoda = {
  \tweak self-alignment-X #RIGHT
  \tweak break-visibility #begin-of-line-invisible
  \myMark \markup { "D.S. al Coda" }
}

theCoda = {
  \tweak self-alignment-X #LEFT
  \tweak break-visibility #end-of-line-invisible
  \myMark \markup { \musicglyph "scripts.coda" }
}

%{
\relative c' {
  c1 c c c \toCoda
  \bar "||" \break
  \mark \default
  c1 c
  \mark \default
  \markDown "23"
  c1 c \DSalCoda
  \bar "||" \break
  \theCoda
  c1 c \DSalCoda
  \bar "||"
  \theCoda
  c1 c
}
%}