LOL here we simply call it plaiting.
Doesn't matter whether you are SJ'ing, Eventing, Dressage, Showing etc the same plaits are used.
The mane is divided and plaited, the end of the plait is folded up to the base of the plait and stitched in place with needle and thread, then you do the same again, end of the plait up to the base of the plait again and stitched. THEN the thread is passed right through the middle of the plait and back again and pulled tight, this gives it a rounder look!
I hope that makes some sense.....