Define shorthand for text spanner, like rit. or rall.
To obtain a textual indication like "rit." or "rall." followed by a dashed line, you have to first set bound-details.left.text. However, it is easy to define a shorthand to both set the text and start the text spanner.
\version "2.24.0"
rit =
\tweak bound-details.left.text #"rit. "
\startTextSpan
rall =
\tweak bound-details.left.text #"rall. "
\startTextSpan
% If you prefer the syntax \rit ... \stopRit:
stopRit = \stopTextSpan
\fixed c' {
c4 d e \rit f |
g1 \stopRit
c4 d e _\rall f |
g1 \stopTextSpan
}