The left tree is built using a query that is ran recursively. One of the clauses of the query makes sure that only folderish documents are displayed (
AND ecm:mixinType = 'Folderish'). The query is defined in the "tree_children" page provider. See below a sample override of this query without the "Folderish" clause. You can contribute to the "providers" extension using the XML Extensions feature.
<require>org.nuxeo.ecm.webapp.pageproviders.contrib</require> <extension target="org.nuxeo.ecm.platform.query.api.PageProviderService" point="providers"> <coreQueryPageProvider name="tree_children"> <property name="maxResults">PAGE_SIZE</property> <pattern> SELECT * FROM Document WHERE ecm:parentId = ? AND ecm:isProxy = 0 AND ecm:mixinType != 'HiddenInNavigation' AND ecm:isCheckedInVersion = 0 AND ecm:currentLifeCycleState != 'deleted' </pattern> <sort column="dc:title" ascending="true" /> <pageSize>50</pageSize> </coreQueryPageProvider> </extension>
You can adapt this sample so as to filter anything you would like to see or not in the left tree.