A MWE:

——
\documentclass{article}

\title{test}
\author{paranda }
\date{December 2024}

\begin{document}

\maketitle
\tableofcontents

\section{Introduction}

\subsection[Sub - shown 1]{Sub intro - shown}
This section shows up with a modified heading
\subsection*{Sub intro - hidden}
This subsection doesn't show up in the ToC
\subsection{Sub intro - shown 2}
This subsection shows up as is in the ToC
\end{document}
——
> El 26 dic 2024, a las 18:08, Pedro Andres Aranda Gutierrez <paaguti@gmail.com> escribió:
>
> Hi Rudolf,
>
> After playing around with the generated LaTeX in overleaf, I have to conclude that the problem is that ALT_TITLE should be not generated for unnumbered chapters, sections, etc. As far as my LaTeX goes, you use the [alt_title] to get something different in the TOC, so it makes no sense and LaTeX doesn’t cater for it.
>
> Solutions from the org-mode side:
> 1. You don’t use ALT_TITLE if section is unnumbered (easier)
> 2. We make org-mode throw an error in this case (???)
>
> Discussion open ;-)
>
> Seasons greetings,
> /PA