Six well-known files means six editors, six previews, six routes — unless something composes them. Admins want one screen: tabs, edit, see the file, save.

XFilesManager is the compound surface: a tab per file kind, each wiring its editor beside its live preview over ONE aggregate XFilesModel (value + onChange). Absent kinds get an Add affordance; kinds / activeKind restrict and control the tabs.

Hold the aggregate model, render <XFilesManager value onChange />, persist on save — the sandbox's /admin/well-known-files page is exactly this component over the fancy-x-files backend.