Yoghurt can be made by holding a small quantity of live yoghurt mixed with fresh milk and stirred and kept at a constant temperature (38C or 100F) for up to 12 hours.
Can the mixture be put in an electric machine (already turned on) to keep it at temperature on Shabbos?
It would seem that there is no problem of “cooking (bishul)” because the temperature is below “yad soledes bo”. (Is it the same for “insulating (hatmonoh)”?).
One problem might be the element of “building (boneh)” involved in cheese-making but the yoghurt has very little structure.