\version "2.12.2"

rechts = \relative c'' {
\textSpannerDown
\override TextSpanner #'(bound-details left text) = "dimin."
\override TextSpanner #'(bound-details left-broken text) = ##f
a1 \startTextSpan a a a \break
a a a a \stopTextSpan
}

rechtsII = \relative c'' {
\textSpannerDown
\override TextSpanner #'(bound-details left text) = "dimin."
\override TextSpanner #'(bound-details left-broken text) = ##f
\once\override TextSpanner #'(bound-details left-broken X) = #8
a1 \startTextSpan a a a \break
a a a a \stopTextSpan
}

links = \relative c' { \clef bass s1*8 }

\new PianoStaff <<
  \new Staff = "up" { \rechts }
  \new Staff = "down" { \links }
>>

\new PianoStaff <<
  \new Staff = "up" { \rechtsII }
  \new Staff = "down" { \links }
>>