Base recipe is one, but every family has additions.
Caraway
1 tsp per kg cabbage. European tradition. Aids digestion.
Apples
1–2 grated tart apples per kg. Sweetness + fermentation boost.
Cranberry
Handful per jar. Vitamin C, pink color, crunchy.
Beet
1 grated beet per kg. Red color, slightly sweet.
Horseradish (spicy)
Grated horseradish to taste. Clears sinuses. Amish cold remedy.
Rule
Add-ins go in with cabbage. Salt 2% of total weight. Everything under brine.