// Get a snapshot of the current configuration ...
RepositoryConfiguration config = engine.getRepositoryConfiguration(repositoryName);
// Now start to make changes ...
Editor editor = config.edit();
// Find the array of sequencer documents ...
List<String> pathToContainer = defn.getPathToContainerOfField();
EditableDocument textExtracting = editor.getOrCreateDocument(pathToContainer.get(1));
EditableDocument extractors = textExtracting.getOrCreateDocument(pathToContainer.get(2));