appendix =
#(define-void-function (parser location title) (markup?)
  (define (appendix-item->markup layout props appendix-item)
    (interpret-markup layout props
      (markup
          #:override (cons 'appendixItem:heading (assoc-ref appendix-item "heading"))
          #:override (cons 'appendixItem:text (assoc-ref appendix-item "text"))
          (ly:output-def-lookup layout 'appendixItemMarkup))))
  (ly:book-add-bookpart! (ly:parser-lookup '$current-book)
  #{
    \bookpart {
      \markup { #title }
      #(for-each
          (lambda (item)
            (add-score (ly:make-page-label-marker (string->symbol (car item))))
            (add-text
              (make-on-the-fly-markup
                (lambda (layout props arg) (appendix-item->markup layout props (cdr item)))
                (make-null-markup)))
          )
        (reverse APPENDIX_DATA))
    }
  #}))

#(define-markup-command (appendix-ref layout props label) (symbol?)
  "call page-ref to appendix-item"
  (interpret-markup layout props
    (markup #:with-link label
      #:override (cons 'appendixPage (make-page-ref-markup label "XXX" "?"))
      (ly:output-def-lookup layout 'appendixReferenceMarkup))))

\paper {
  appendixItemMarkup = \markup {
    \left-column {
      \line { \large \bold \fromproperty #'appendixItem:heading }
      \vspace #0.2
      \sans \wordwrap-field #'appendixItem:text
      \vspace #0.7
    }
  }
  appendixReferenceMarkup = \markup {
    \fromproperty #'appendixPage
  }
}