- @ HoMe : No, Cinema 4D doesn't seem to be able to import 3DM (or IGES) files. If you're able to do that, please explain how.

- @ Michael : Dragging the (imaginary) sliders in both the UI options dialog box or the export mesh dialog box doesn't make any change (and it also doesn't work with multiple clicks in the area)

Also, on my other computer I noticed that OBJ export is some kind of "all or nothing". If the slider is put to the left, I've a low poly version. Then if I drag to the right I've a high poly version but no gradation between the two. The file size and the number of polygons is the same when I export an object with the slider at the middle of the bar or if the slider is at the extreme right.
As you mentioned that export is still a "work in progress" it's difficult to know if it's normal (for now on) or if it's something to report ?