The current den migration guide suggests you switch to den, and import your existing configuration into it using import-tree.
However, this can be very cumbersome because it changes your flake wiring and requires you to change your folder structure and figure out how to deal with your special args right away.
Or maybe I just misunderstood the guide.
Anyway, this guide reverses it and makes you keep your existing configuration, adding den modules on top of it.
