Arrow between measures

To put an arrow between separated measures, try this code:

\version "2.24"

arrow = 
  -\tweak Y-offset #0
  -\tweak outside-staff-priority ##f
  -\markup
  \concat {
    \draw-line #'(5 . 0)
    \hspace #-0.2 % This is to bridge the small indentation in the arrow-head
    \arrow-head #X #RIGHT ##t
  }
  
\new Staff {
  c''1 \stopStaff << \tweak transparent ##t R1-\arrow >> \startStaff c''1
}