Knowledge Base: show articles nested under folders in a top-level tree view

Today the Knowledge Base (Central KB and company KB) shows an expandable folder-only tree with article counts. Expanding a folder reveals child folders, not article titles. Articles appear in a separate flat table: at the top level that table is only unfiled articles; inside a folder it is only articles in that folder. Search/label filters can list articles across folders, but still as a flat table (and the folder tree is hidden).