Adjusting grace note spacing

The space given to grace notes can be adjusted using the spacing-increment property of Score.GraceSpacing.

\version "2.24.0"

graceNotes = {
  \grace { c4 c8 c16 c32 }
  c8
}

\relative c'' {
  c8
  \graceNotes
  \override Score.GraceSpacing.spacing-increment = #2.0
  \graceNotes
  \revert Score.GraceSpacing.spacing-increment
  \graceNotes
}