Settings editor 

When the site sets of indexed_search are included, the settings provided by those sets become available in the editor.

You can find the available site settings in module Sites > Setup > Settings

You can change individual settings here. If the site settings are writable you can hit the Save button and the settings will be written directly to the site settings.

If the settings are not writable you can click the YAML export button to export the settings. These can then be added by a developer with sufficient rights.

The available settings are also described in detail in chapter Site set "Indexed Search".