This question has been asked before, but for a different beamer theme. The answer there did not make it clear to me how to deal with my case, illustrated in this example (which I think is close to minimal):

\documentclass[compress]{beamer}
\usetheme{Singapore}
\useoutertheme{miniframes}
% ^ dots up top
% ^ disable annoying footer
\newcommand{\mytoc}{
\tableofcontents[
currentsubsection,
hideothersubsections,
]}
\newcommand{\mytocslide}{
\begin{frame}
\mytoc
\end{frame}}
\begin{document}
\section{Introduction}\subsection{}
\begin{frame}{hiya}
yo
\end{frame}
\mytocslide
\section{Second section}\subsection{}
\begin{frame}
yoyo
\end{frame}
\begin{frame}
yoyoyo
\end{frame}
\end{document}


The resulting document includes the extra section in the TOC but not the nav bar (as desired), but it looks weird in the TOC.

-
–  Frank Jan 20 at 1:53
See this question and the answer. \section inserts a new entry into the table of contents at the appropriate tree-level and also inserts a new entry into the navigation bars. But \section* only adds an entry in the navigation bars, not in the table of contents. –  Masroor Jan 20 at 2:06
When you say it 'looks weird', could you elaborate? What should it look like? It looks fine to me although it is not a link as the other entries are. Is that what you mean? –  cfr Jan 20 at 2:07
@cfr Sorry, I didn't think to actually include a picture. You are correct, I meant that I expected it to show up blue (like a link) and similarly spaced to the other entries. –  Frank Jan 20 at 3:11
@MMA Thanks, I knew that question was related (see my comment above yours :) ), but it does not solve the problem at hand. –  Frank Jan 20 at 3:11

To achieve the same formatting as a regular section entry, you need some additional work: section entries in the ToC have a vertical extra spacing of 1.5em and they have a special color, so you need to say something like:

\addtocontents{toc}{\vskip1.5em}


A complete example:

\documentclass[compress]{beamer}
\usetheme{Singapore}
\useoutertheme{miniframes}
\newcommand{\mytoc}{
\tableofcontents[
currentsubsection,
hideothersubsections,
]}
\newcommand{\mytocslide}{
\begin{frame}
\mytoc
\end{frame}}

\begin{document}
\section{Introduction}
\subsection{}
\begin{frame}{hiya}
yo
\end{frame}
\mytocslide

\section{Second section}
\subsection{}
\begin{frame}
yoyo
\end{frame}

\begin{frame}
yoyoyo
\end{frame}

\end{document}


An image of the resulting ToC, showing the new additional entry, not present in the navigation bar:

A more robust solution (that doesn't require manual intervention and that will even give you an hyperlink) can be achieved by defining a new command using the exact way in which sections are included in the ToC (the relevant definition can be found in the file beamerbasesection.sty):

\documentclass[compress]{beamer}
\usetheme{Singapore}
\useoutertheme{miniframes}
\newcommand{\mytoc}{
\tableofcontents[
currentsubsection,
hideothersubsections,
]}
\newcommand{\mytocslide}{
\begin{frame}
\mytoc
\end{frame}}

\makeatletter
\protect\beamer@sectionintoc{\the\c@section}{#1}{\the\c@page}{\the\c@part}%
{\the\beamer@tocsectionnumber}}
}
\makeatother

\begin{document}

\section{Introduction}
\subsection{}
\begin{frame}{hiya}
yo
\end{frame}
\mytocslide

\section{Second section}
\subsection{}
\begin{frame}
yoyo
\end{frame}


Thank you! I did not realize that I could customize the appearance of the TOC line. It looks like I can do both steps in one: \addcontentsline{toc}{section}{\vskip1.5em\protect\usebeamercolor[fg]{structure‌​} Conclusion} –  Frank Jan 20 at 3:09