\version "2.23.4"

\paper {
  indent = 1 \in
  short-indent = 1 \in
}

\layout {
  \context {
    \Staff
    \RemoveAllEmptyStaves
  }
}

music = \repeat unfold 4 { c'1 }
rests = \repeat unfold 4 { R1 }

\score {
  <<
    \new Staff \with {
          instrumentName = "0"
          shortInstrumentName = "0"
        } {
          \music \break
          \music \break
          \music
        }
    \new StaffGroup \with {
      \consists "Keep_alive_together_engraver"
    } {
      <<
        \new Staff \with {
          instrumentName = "1"
          shortInstrumentName = "1"
        } {
          \rests
          \rests
        }

        \new StaffGroup \with {
          systemStartDelimiter = #'SystemStartBrace
        } {
          <<
            \new Staff \with {
              instrumentName = "2a"
              shortInstrumentName = "2a"
            }
            {
              \music
              \music
            }
            \new Staff \with {
              instrumentName = "2b"
              shortInstrumentName = "2b"
            }
            {
              \music
              \rests
            }
          >>
        }

        \new StaffGroup \with {
          systemStartDelimiter = #'SystemStartBrace
        } {
          <<
            \new Staff \with {
              instrumentName = "3a"
              shortInstrumentName = "3a"
            }
            {
              \rests
              \rests
            }
            \new Staff \with {
              instrumentName = "3b"
              shortInstrumentName = "3b"
            }
            {
              \rests
              \rests
            }
          >>
        }
      >>
    }
  >>
}