Label inside tikzcd square

Question

I have part of a diagram with tikzcd which looks like this:

\begin{tikzcd}[column sep=20mm]
A\ar[rd,"a"] & \\
B\ar[rd,"b"]\ar[u,"b"] & C \\
& D\ar[u,"d"]
\end{tikzcd}

and produces the following

Now, I want to add a text in the middle of this diagram, and with the same inclination than it. The only way that I got to produce this, was to embed the tikzcd inside a tikzpicture:

\begin{tikzpicture}
  \node {\begin{tikzcd}[column sep=20mm]
      A\ar[rd,"a"] & \\
      B\ar[rd,"b"]\ar[u,"b"] & C \\
      & D\ar[u,"d"]
  \end{tikzcd}};
  \node[rotate=-25] {Text};
\end{tikzpicture}

Is there any way to produce the same within the tikzcd environment?

Answer 1

Using this answer there is no need to nest tikzpictures, which you are effectively doing when putting a tikzcd environment into a node of a tikzpicture.

\documentclass{article}
\usepackage{tikz-cd}
\begin{document}  
\[  \begin{tikzcd}[column sep=20mm,
  execute at end picture={
    \path (\tikzcdmatrixname-1-1) -- (\tikzcdmatrixname-2-1)
    coordinate[pos=0.5] (aux1)
    (\tikzcdmatrixname-2-2) -- (\tikzcdmatrixname-3-2)
    coordinate[pos=0.5] (aux2)
    (aux1) -- (aux2) node[midway,sloped]{Text};
  }]
      A\ar[rd,"a"] & \\
      B\ar[rd,"b"]\ar[u,"b"] & C \\
      & D\ar[u,"d"]
  \end{tikzcd}\]
\end{document}

Answer 2

Another solution from within tikz-cd:

\documentclass{article}
\usepackage{amsmath}
\usepackage{tikz-cd}

\begin{document}

\begin{tikzcd}[column sep=20mm]
A\ar[rd,"a"] \ar[rd, phantom, shift right=3.4ex, "\quad\text{Text}" marking]& \\
B\ar[rd,"b"]\ar[u,"b"] & C \\
& D\ar[u,"d"]
\end{tikzcd}

\end{document}