Vertically aligning stanza numbers of different staves

It can happen that stanza numbers don't align vertically if the verses are attached to different staves. To fix that, override the self-alignment-X property of the LyricText grob.

\version "2.24.0"

\markup { default behavior }

<<
  \new Staff { b b b b }
  \lyrics {
    \set stanza = "3."
    a a a a
  }

  \new Staff { b b b b }
  \lyrics {
    \set stanza = "1."
    aaaaaaaaaa a a a
  }
  \lyrics {
    \set stanza = "2."
    a a a a
  }
>>

\markup \vspace #1
\markup {
  using \typewriter "self-alignment-X = #LEFT" }

<<
  \new Staff { b b b b }
  \new Lyrics \lyricmode {
    \set stanza = "3."
    a a a a
  }

  \new Staff { b b b b }
  \new Lyrics \lyricmode {
    \set stanza = "1."
    \once \override LyricText.self-alignment-X = #LEFT
    aaaaaaaaaa a a a
  }
  \new Lyrics \lyricmode {
    \set stanza = "2."
    a a a a
  }
>>

\paper { tagline = ##f }