documentclass{scrartcl}
usepackage{titletoc}

begin{document}

startcontents
printcontents{ }{1}{}

section{A Regular Section}
subsection{First subsection}
subsubsection{Subsubsection one one}
subsubsection{Subsubsection one two}

appendix

section{A Long Appendix}
stopcontents

startcontents[sections]
printcontents[sections]{ }{2}{}

subsection{First subsection in Appendix}
subsubsection{Subsubsection one one in Appendix}
subsubsection{Subsubsection one two in Appendix}

subsection{Second subsection in Appendix}
subsubsection{Subsubsection two one in Appendix}
subsubsection{Subsubsection two two in Appendix}
stopcontents[sections]

resumecontents
section{A short appendix}
subsection{First subsection in short appendix}
subsubsection{First subsubsection in short appendix}

end{document}

startcontents
renewcommandcontentsname{Table of Contents}% if a change of the default "Contents" name is required
printcontents{ }{1}{section*{contentsname}}

startcontents[sections]
renewcommandcontentsname{Table of my Long Appendix}
printcontents[sections]{ }{2}{subsection*{hspace*{1.2em}contentsname}}

documentclass{scrartcl}
usepackage{etoc}

begin{document}

tableofcontents

section{A Regular Section}
subsection{First subsection}
subsubsection{Subsubsection one one}
subsubsection{Subsubsection one two}

appendix

etocsettocdepth.toc{section}% will be obeyed by main TOC

section{A Long Appendix (with its own TOC)}

etocignoretoctocdepth % of course, if we want to see something in local TOC...
etocsettocstyle{subsection*{contentsname}}{}
localtableofcontents

subsection{First subsection in Appendix}
subsubsection{Subsubsection one one in Appendix}
subsubsection{Subsubsection one two in Appendix}

subsection{Second subsection in Appendix}
subsubsection{Subsubsection two one in Appendix}
subsubsection{Subsubsection two two in Appendix}

etocsettocdepth.toc{subsubsection}% will be obeyed by main TOC
section{A short appendix}
subsection{First subsection in short appendix}
subsubsection{First subsubsection in short appendix}

end{document}