1. Install Firefox.
2. Log in to fresh Firefox instance.
3. Let browser-wide sync happen.
4. Sync installs multi-account containers addon.
5. Four empty default containers are created. New user welcome flow is active.
6. Sign in to multi-account containers addon. Wait for container sync to do its thing.
7. Containers sync invisibly in the background.
- Default containers that you deleted before (in the instance you are syncing from) still exist in this fresh instance.
- New user welcome UX is still active.