Beamer miniframes: A single active navigation bullet for two consecutive frames

Question

In a beamer presentation with miniframes, I would like to combine two frames to give just one navigation bullet. This navigation bullet should be active (i.e., filled) when the presentation is currently on either of the two frames.

Basically, the question is as the one here and the answer here, except that there the navigation bullets are not "active" (i.e., filled) for the frames that are not counted.

E.g., I have 4 frames and like to have something like

\frame{1}
\startcombine
\frame{2}
\frame{3}
\endcombine
\frame{4}

and then the navigation bar should show "x o o" on the first frame, "o x o" on the second and third frame, and "o o x" on the fourth frame", where "x" are the "active" (i.e., filled) bullets.

Answer 1

If you don't want to create a new miniframe, don't start a new frame. Instead you can use overlays to have the content of two different slides in a single frame:

\documentclass{beamer}

\usetheme{Darmstadt}

\begin{document}

\section{section}

\begin{frame}

  \frametitle<1>{First frame}
  \begin{onlyenv}<1>
  Content for the first frame
  \end{onlyenv}
  
  \frametitle<2>{Second frame}
  \begin{onlyenv}<2>
  Content for the second frame
  \end{onlyenv}

\end{frame}
  
\end{document}