minecraft-assets/data/minecraft/recipe/muddy_mangrove_roots.json

{
  "type": "minecraft:crafting_shapeless",
  "category": "building",
  "ingredients": [
    "minecraft:mud",
    "minecraft:mangrove_roots"
  ],
  "result": {
    "count": 1,
    "id": "minecraft:muddy_mangrove_roots"
  }
}