To enable expert settings you first have to enable Expert Mode

Content settings

Additional settings are displayed in the project settings:

Files

Here you can upload any files (styles, scripts, assets, etc.). Script and style files are inserted into the page when it loads. Other files are transferred to the clients and can then be referenced in your custom scripts and styles.

Experimental features

Here the experimental feature Layers can be activated.

Advanced JSON settings

Here various internal JSON settings can be edited manually.

Edit mode

In addition to normal editing, expert editing allows properties to be changed without validation.