This documentation is not using the current rendering mechanism and is probably outdated. The extension maintainer should switch to the new system. Details on how to use the rendering mechanism can be found here.
Adding file metadata to the search index
Adding a document to the search index
Documents within a site root can be individually added to the search index, an entry is added or updated in the Solr index queue upon saving.
When a selection is removed or a document is deleted from the file list, it is automatically removed from the Solr index.