Hi Pilou,

re:
> Why it's obligatory to save the object then reload it for SubD create from a file ?

Mostly because generally the result of converting a NURBS object into a mesh is not suitable for a good quality subdivision smoothing.

But in the future I do want to expand the options for creating SubD objects, that's why the SubD button pops up a menu even though there is only one thing on it currently. When I have time to work on it I would like to add more entries there.

If you examine your model you show in more detail you will likely see a lot of bad shaping, things like some areas pinched or stretched awkwardly. It's not really a priority to make it super easy to make something that's likely to be badly formed...

- Michael