If you like to organize your notes into a lot of separate folders, then folder notes might be something for you.

toggles:
  features:
    folder_notes:
      enabled: True
      placement: 'outside folder'   # 'inside folder' , 'outside folder' 
      naming: 'folder name'           # 'folder name', 'index', 'aurkibidea', 'etc'

Example

On this site, the folders Changelog, Styling, and Demonstrations have an associated folder note. This results in the little triangle on the left. When clicking the folder, instead of opening the folder in the navigation, the associated note is opened.

Important notices

Folder notes are not included by default unless Process All is enabled.

When this setting is disabled, as is default, make sure that there is a link-chain from your entrypoint to each folder note that you want to end up in your html output.

So for example:
index.md --> mocs.md --> folder1/index.md, folder2/index.md, etc

Inside/outside

You can set your files like this:

│   Changelog
│   ├── Changelog.md
│   └── v1.0.0.md

In that case you should set placement: 'inside folder'

Conversely, for this setup:

│   Changelog
│   └── v1.0.0.md
│   Changelog.md

You should set placement: 'outside folder'

Naming

You can either set naming to 'folder note', or anything else. When the value is literally 'folder note', the name of the corresponding folder is used, otherwise ObsidianHtml will search for a file called {naming}.html.

In the first example of the previous section, the folder note had the same name as the folder, if you want to use index for every note, like so:

│   Changelog
│   ├── index.md
│   └── v1.0.0.md

You should set:

toggles:
  features:
    folder_notes:
      enabled: True
      placement: 'inside folder'  
      naming: 'index'           

Breadcrumbs

If you are using folder notes, you might also be interested in Breadcrumbs.