Nested star lists for GitHub collects nothing.

• No data leaves your browser. The extension reads the GitHub pages you are
  already looking at and rearranges them locally. There is no server, no
  analytics, no telemetry, and no network request to anything but
  github.com — and those are the same-origin requests the page itself could
  make.
• Settings stay yours. The three options (sort order, folders expanded,
  full list names) are stored with your browser's own extension-settings
  storage (storage.sync), which your browser may sync between your devices.
  Nothing else is stored.
• A per-tab cache. The parsed list index is kept in the tab's
  sessionStorage so the rail paints instantly; it dies with the tab.