How to change TOC depth in R Bookdown (GitBook)?

Question

I use GitBook format through R bookdown. I need to use at least four levels in the table of contents (TOC). The default is three. How can I change the depth of TOC?

---

UPDATE

Now the toc-related contents of my _output.yml file look like this:

bookdown::gitbook:
  config:
    toc_depth: 4
    toc:
      collapse: section
      scroll_highlight: yes
      before: |
        <li><a href="../index.html"><b>Main</b></a></li>
      after: |
        <li><a href="../index.html"><b>Main</b></a></li>

config: toc_depth: 4 does not work.

Answer 1

Try adding the following to your _output.yml file:

bookdown::gitbook:
    toc_depth: 2