minecraft-assets/data/minecraft/worldgen/placed_feature/pale_moss_patch.json

{
  "feature": "minecraft:pale_moss_patch",
  "placement": [
    {
      "type": "minecraft:count",
      "count": 1
    },
    {
      "type": "minecraft:in_square"
    },
    {
      "type": "minecraft:heightmap",
      "heightmap": "MOTION_BLOCKING_NO_LEAVES"
    },
    {
      "type": "minecraft:biome"
    }
  ]
}