After the growing season, from the winter when the cuttings were made, until the following autumn when these photos were taken, approximately 10 months passed.
In the following photos, we see one of the cuttings that rooted well despite the aerial part having barely developed. It grew two pairs of leaves, enough to feed the little plant. In this pot of four cuttings, only this one rooted, but I think that with a little more zeal during spring and summer, the other three would also be able to root.

After carefully removing it from the pot, we can see the fine white roots.

Finally, I plant the new Japanese snowball plant in an individual pot and hope that it will grow vigorously next year.

(Sorry for the poor quality of these last few photos.)
I will update this article with new photos once this plant grows into spring.