Me ha contestado Nicolas Auffray, diciéndome que no había entendido correctamente lo de buscar la carpeta. Que siempre se ha de importar para que darktable pueda relacionar las imágenes.
Le he contestado que tal vez mi ingles no era el mas idoneo pero que Nilvus habia sugerido que si lo hacia (tal como expresabas mas arriba) Veremos que me contesta, pero ha sido claro.
Dejo la contestación por si hay algo que se me haya escapado.
Hi,
You certainly not understand correctly what I suggest. I not only suggest the right-click and then research a filmroll but also to manage files only in darktable. And never outside. I always manage my files inside darktable without any problems (and since more than 3 years that I use intensively darktable. And I'm not the only one to use it that way without any problem.
darktable link files from your filesystem, so of course if you break links, you will have issues. If you add/remove files directly from darktable (by using import options to add and remove/delete from related module in right panel), you will never had issues. If you change them outside darktable, you will always have issues.
As for each tool, just use it the good way and all will be good. If necessary, the manual is here to help.