% http://lists.gnu.org/archive/html/lilypond-user/2018-05/msg00099.html

tenutoFingeringMark = \markup \text \fontsize #2 \bold "t"
t = #(define-event-function (n) (index?)
  #{ \finger \markup \concat { #(format #f "~d" n) \tenutoFingeringMark } #})

{
  c'4\t3 e'_\t1 a'2-\t2
}