topnush
Take the following MWE with commented out parts.
```
\documentclass{beamer}
\beamertemplatenavigationsymbolsempty
\setbeamersize{text margin left=10mm,text margin right=5mm}
\setbeamertemplate{frametitle}[default][center]
\usepackage[many]{tcolorbox}
\usepackage{mathrsfs}
\usepackage{adjustbox}
\usepackage{accents}
\usepackage{mathtools}
\usepackage{bm}
\usepackage{tikz}
\usetikzlibrary{arrows.meta,bending,tikzmark,overlay-beamer-styles}
% if you wish to annotate listings without modifying their source:
% \usetikzmarklibrary{listings}
\tikzset{show on/.style={inner sep=1pt,draw=purple,rounded
corners,fill=red!20,visible on=<#1>,text opacity=1}}
\usetikzlibrary{shapes.geometric, patterns,decorations.pathreplacing, calligraphy}
\newenvironment{grayenv}{\only{\setbeamercolor{local structure}{fg=black!15}}}{}
\DeclareMathOperator{\supp}{supp}
\begin{document}
\begin{frame}[t, fragile]
\frametitle{frame title}
\setbeamertemplate{itemize items}[circle]
\addtolength{\leftmargini}{-0.7cm}
\begin{itemize}[<+-|gray@+(1)->]
\setlength\itemsep{5pt plus 1fill}
\item Some text
\item $\begin{aligned}[t]
\MoveEqLeft[1]\Pr(\text{vector fed to some more text-sparse}) \\
%\visible<+->{\tikzmarknode[show on={2-3}]{fai}{&= \Pr(\text{Some text is selected and no other text is})\\}}
\visible<+->{&=\smashoperator{\sum_{j \in \supp \bm{f}}}\;\;\Pr(X=\bm{0})\cdot \Pr(\text{no other text is selected}\mid X = \bm{0} )\\}
\visible<+->{&=\smashoperator{\sum_{j \in \supp \bm{f}}} \;\;\Pr(j\text{ is selected and no other text is})}
\end{aligned}$
\end{itemize}
%\begin{tikzpicture}[remember picture, overlay,visible on=<5>]
% \draw[dashed,{Stealth[bend]}-] (fai.south) to [out=-90,in=90]++ (-1.5,-2) node[align=left, below, rectangle,draw, rounded corners, solid, fill=green!30]{explanatory text};
% \end{tikzpicture}
\end{frame}
\end{document}
```
I want to make a text box and point from there to the commented out line. If you comment out the commented parts it doesn't render however.