Space between conclusion and appendices in ToC

Question

I would like to add some space between conclusion chapter and the first appendix in ToC. I'm already using \setlength{\cftbeforechapskip} to adjust vertical length of the space between ALL chapters in ToC. My code is

\documentclass[a4paper,12pt]{book}
\usepackage[titles]{tocloft} %changing vertical length of the space between ALL chapters
                             %entries in ToC via \setlength{\cftbeforechapskip}{1pt}

\begin{document}

\frontmatter
\setlength{\cftbeforechapskip}{6pt} 
\tableofcontents


\mainmatter
\chapter*{Introduction}
\addcontentsline{toc}{chapter}{Intro}

\chapter{aaaaaaaaaaaaaaaaaaaaaaaaaaaaa}
\section{111111}
\section{222222}
\section{3333333}
\chapter{bbbbbbbbbbbbbbbbbbbbbbbbbbbbb}
\section{111111}
\section{222222}
\section{3333333}
\section{4444444}
\section{5555555}
\section{6666666}
\chapter{ccccccccccccccccccccccccccccccccccc}
\section{111111}
\section{222222}
\section{3333333}

\chapter*{Conclusion}
\addcontentsline{toc}{chapter}{Conclu}


\appendix
\chapter{aaaaaaa}
\chapter{bbbbbbbb}
\chapter{ccccccccc}

\end{document}

And the picture to make things more clear,

Cheers!

Answer 1

You can use

\addtocontents{toc}{\protect\vskip<length>}

with the desired value for <length>:

\documentclass[a4paper,12pt]{book}
\usepackage[titles]{tocloft} %changing vertical length of the space between ALL chapters
                             %entries in ToC via \setlength{\cftbeforechapskip}{1pt}

\begin{document}

\frontmatter
\setlength{\cftbeforechapskip}{6pt} 
\tableofcontents


\mainmatter
\chapter*{Introduction}
\addcontentsline{toc}{chapter}{Intro}

\chapter{aaaaaaaaaaaaaaaaaaaaaaaaaaaaa}
\section{111111}
\section{222222}
\section{3333333}
\chapter{bbbbbbbbbbbbbbbbbbbbbbbbbbbbb}
\section{111111}
\section{222222}
\section{3333333}
\section{4444444}
\section{5555555}
\section{6666666}
\chapter{ccccccccccccccccccccccccccccccccccc}
\section{111111}
\section{222222}
\section{3333333}

\chapter*{Conclusion}
\addcontentsline{toc}{chapter}{Conclu}

\appendix
\addtocontents{toc}{\protect\vskip30pt}
\chapter{aaaaaaa}
\chapter{bbbbbbbb}
\chapter{ccccccccc}

\end{document}

The \addtocontents line has to be placed before the \chapter line of the first chapter in the appendices; if you use \include to pull the chapters together, the \addtocontents instruction has to go into the chapter file, just before the \chapter line; otherwise, the added space might result in the wrong place.