In the following output, I would like the texts "ou" to be aligned with the first line of each cell. Maybe a yshift can do the job. But in that case, which length should be preferred?
Here is the M(erely)WE used.
\documentclass[varwidth, border = 3pt]{standalone}
\usepackage{witharrows}
\usepackage{tabularray}
\UseTblrLibrary{tikz}
\newcommand\testit{
\begin{WithArrows}[right-overlap = false, format = l]
f(x) \ge g(x) \Arrow{S1} \\
f(x)^2 \ge g(x)^2 \Arrow{S2} \\
f(x)^2 - g(x)^2 \ge 0
\end{WithArrows}
}
\begin{document}
\begin{tblrtikzabove}
\node at (v2) [fill=white, inner sep=2pt] {ou};
\node at (v3) [fill=white, inner sep=2pt] {ou};
\end{tblrtikzabove}%
\begin{tblr}{
vline{2-Y},
colsep = 10pt,
cells = {mode = math}
}
\testit
& ABC
& \testit
\end{tblr}
\begin{tblrtikzabove}
\node at (v2) [fill=white, inner sep=2pt] {ou};
\node at (v3) [fill=white, inner sep=2pt] {ou};
\end{tblrtikzabove}%
\begin{tblr}{
vline{2-Y},
colsep = 10pt,
cells = {mode = math}
}
A & B & C
\\
A & B & C
\end{tblr}
\end{document}


yshiftcan do the job. But in that case, which length should be preferred?