%%
%% The LaTeX Companion, 3ed
%%
%% Example 2-2-22 on page I-54 in "Formatting headings --- \LaTeX 's internal low-level methods".
%%
%% Copyright (C) 2022 Frank Mittelbach
%%
%% It may be distributed and/or modified under the conditions
%% of the LaTeX Project Public License, either version 1.3c
%% of this license or (at your option) any later version.
%%
%% See https://www.latex-project.org/lppl.txt for details.
%%

\documentclass{tlc3exa}
\pagestyle{empty}
\setcounter{page}{6}
\setlength\textwidth{183.0pt}

\makeatletter
\renewcommand\appendix{%
   \renewcommand\section{%                     Redefinition of \section...
        \newpage\thispagestyle{plain}%           new page, folio bottom
        \suppressfloats[t]\@afterindentfalse%    no top floats, no indent
        \secdef\Appendix\sAppendix}%
   \setcounter{section}{0}\renewcommand\thesection{\Alph{section}}}
\newcommand\Appendix[2][?]{%   Complex form
   \refstepcounter{section}%
   \addcontentsline{toc}{appendix}{\protect\numberline{\appendixname~\thesection}#1}%
   {\raggedleft\large\bfseries\appendixname\ \thesection\par \centering#2\par}%
   \@afterheading\sectionmark{#1}\addvspace{\baselineskip}}
\newcommand\sAppendix[1]{%           Simplified (starred) form
  {\raggedleft\large\bfseries\appendixname\par \centering#1\par}%
  \@afterheading\addvspace{\baselineskip}}
\makeatother

%StartShownPreambleCommands
% Example needs commands introduced above!
%StopShownPreambleCommands

\begin{document}
\appendix
\section{The list of all commands}

Then follows the text of the first section in
the appendix. Some more text in the appendix.
\end{document}
