I use Lyx 2.1, class document : report. I created a general introduction as unnumbered chapter, but at the table of Contents, the introduction does not exist.

• – Werner Jun 24 '14 at 22:47

There is no formal LyX way to insert general content into the Table of Contents (ToC) other than using an ERT (the (La)TeX way). As such, you should insert an ERT containing

``````\addcontentsline{toc}{chapter}{General Introduction}
``````

immediately after you've inserted the chapter. For alignment purposes (of the numbers in the ToC), you could also use

``````\addcontentsline{toc}{chapter}{\numberline{}General Introduction}
``````

One could modify the LaTeX preamble to always insert an unnumbered chapter into the ToC by adding the following:

``````\usepackage{xparse}% http://ctan.org/pkg/xparse
\let\oldchapter\chapter
\RenewDocumentCommand{\chapter}{s o m}{%
\IfBooleanTF{#1}
{\oldchapter*{#3}% \chapter*
\IfNoValueTF{#2}