How to use custom highlighting themes

I have been trying to use a custom highlighting theme but I am not sure if I am setting it up correctly. According to the documentation:

Alternatively, the extra_syntaxes_and_themes configuration option can be used to add additional theme files. You can load your own highlight theme from a TextMate .tmTheme file.

It works the same way as adding extra syntaxes. It should contain a list of paths to folders containing the .tmTheme files you want to include. You would then set highlight_theme to the name of one of these files, without the .tmTheme extension.

If your site source is laid out as follows:

├── config.toml
├── content/
│   └── ...
├── static/
│   └── ...
├── highlight_themes/
│   ├── MyGroovyTheme/
│   │   └── theme1.tmTheme
│   ├── theme2.tmTheme
└── templates/
  └── ...

you would set your extra_highlight_themes to ["highlight_themes", "highlight_themes/MyGroovyTheme"] to load theme1.tmTheme and theme2.tmTheme . Then choose one of them to use, say theme1, by setting highlight_theme = theme1 .

but I am not sure about how exactly the configuration file should look like, since neither extra_syntaxes_and_themes nor extra_highlight_themes appear on the configuration doumentation.

My current folder structure is the following:

├── config.toml
├── extra-highlight-themes
│   └── modified-nord.tmTheme
├── content
├── public
├── sass
├── static
└── templates

and my configuration:

highlight_code = true

extra_highlight_themes = ["extra-highlight-themes",]
highlight_theme = "modified-nord"

This configuration pass the zola check and work when built locally and when I run zola serve, but it doesn’t work with the zola deploy github action. The fact that it works locally makes me think that it is due to a problem with the action but I wanted to make sure that the configuration file is right and I couldn’t find any more information in the zola documentation.