I'm a really big fan of this presentation style
https://www.archer.ac.uk/training/course-material/2014/04/PMMP_UCL/Slides/castep_1.pdf
and I'm wondering if anyone has come across the sort of clickable+expanding/minimizing legend used on the left hand side of each slide. I haven't been able to find on the TeX exchange so far this exact kind of legend type.
This is probably not the best solution but you can use \useoutertheme[hideothersubsections,left]{sidebar} to hide the subsections of not selected subsections and use:
\usepackage{hyperref}
\hypersetup{
linktoc=all, %set to all if you want both sections and subsections linked
}
to make the table of content clickable.
Here is an example:
\documentclass[a4paper]{beamer}
\usetheme{Boadilla}
\useoutertheme[hideothersubsections,left]{sidebar} %hides the subsetions of not selected sections
\usepackage{color}
\usepackage{hyperref}
\hypersetup{
linktoc=all, %set to all if you want both sections and subsections linked
}
\title{Amazing Presentation}
\author{By Me}
\date{\today}
\begin{document}
\begin{frame}[plain]{}
\titlepage
\end{frame}
\begin{frame}[plain, allowframebreaks]
\tableofcontents
\end{frame}
\section{Section 1}
\subsection{A subsection}\begin{frame}{}\end{frame}
\subsection{Another subsection}\begin{frame}{}\end{frame}
\subsection{So many subsections}\begin{frame}{}\end{frame}
\section{Section 2}
\subsection{Even more subsections!}\begin{frame}{}\end{frame}
\subsubsection{Subsubsections are possible as well}\begin{frame}{}\end{frame}
\subsubsection{Amazing!}\begin{frame}{}\end{frame}
\subsection{The subsections are even clickable}\begin{frame}{}\end{frame}
\subsection{I think you get the point}\begin{frame}{}\end{frame}
\end{document}
Result:
If you want to, you can customize the sidebar
I got the idea of using frames this way from here.
