您只需添加dashed
选项:
\documentclass[border=3.141592]{standalone}
\usepackage{tikz-cd}
\begin{document}
\begin{tikzcd}[labels={font=\scriptsize, pos=0.51}]
X \ar[d, Rightarrow, dashed] \\ % <---
Y \ar[d, bend left, "g"]
\ar[d, bend right, "f" '] \\
Z
\end{tikzcd}
\end{document}