I wasn't able to find what I need in there, but I did find this elsewhere:
If you want to add a document chapter that has no a chapter number but appearing inside the table of content, the classical LATEX commands \chapter and \chapter* are inefficient. Indeed, \chapter add a numbered chapter inside the table of content, and \chapter* adds an unnumbered chapter but not inside the table of content.
To add a unnumbered chapter inside the table of content, you could use one of the commands:
\chaptertoc[toctitle]{title}
\chaptertoc*[toctitle]{title}
The commands
\chaptertoc and \chaptertoc* have the same effect except that \chaptertoc* aligns the chapter’s title to the other numbered chapters’ titles; and \chaptertoc not.
But I get an error message:
Undefined control sequence.
1.6 \chaptertoc
*[toctitle]{title}
I assume the new command replaces the existing chapter command, right?