Add to a Droplist or Wire a New One

Droplists live in Server/Drops/. A block points at one by id, and breaking the block rolls that list. You want a block to drop something extra, or to drop from a list you authored. There are two distinct tasks here, and only one of them is a patch each time.

Goal

• Goal 1: gravel keeps its stock drop but also has a chance to roll a PortalKey_Maze_Var1, but only when Icarus:EchoOfIcarus is present.
• Goal 2: a block you do not own should drop from a brand-new droplist you wrote.

The Original Asset

Without Patchly, changing one entry means your override file has to restate the whole asset, because Hytale does not deep-merge nested blocks. Here are the entire real files you would copy and maintain the old way, with the parts you actually wanted marked.

For Case 1, the stock gravel droplist at Server/Drops/Soil_Gravel.json:

{
  "Container": {
    "Type": "Multiple",
    "Containers": [ // you want to ADD one more drop here, not replace what is here
      {
        "Type": "Single",
        "Item": {
          "ItemId": "Rubble_Stone",
          "QuantityMax": 2,
          "QuantityMin": 1
        }
      }
    ]
  }
}

For Case 2, a real block that references a droplist by id, the entire Server/Item/Items/Soil/Gravel/Soil_Gravel_Sand.json:

{
  "Parent": "Soil_Gravel",
  "TranslationProperties": {
    "Name": "server.items.Soil_Gravel_Sand.name"
  },
  "Icon": "Icons/ItemsGenerated/Soil_Gravel_Sand.png",
  "Categories": [
    "Blocks.Rocks"
  ],
  "Set": "Rock_Sandstone",
  "BlockType": {
    "Textures": [
      {
        "All": "BlockTextures/Soil_Gravel_Sand.png",
        "Weight": 1
      }
    ],
    "Gathering": {
      "Breaking": {
        "GatherType": "Soils",
        "DropList": "Rubble_Sandstone" // you want to point this at your own list
      }
    },
    "ParticleColor": "#c69f4f",
    "TransitionTexture": "BlockTextures/Transition_Gravel_Sand.png"
  }
}

The patch

Case 1 - add a drop to an existing list

Patch at Server/Drops/Soil_Gravel.patch:

{
  "$Requires": "Icarus:EchoOfIcarus",
  "Container": {
    "Containers+": [
      {
        "Type": "Single",
        "Item": {
          "ItemId": "PortalKey_Maze_Var1",
          "QuantityMax": 1,
          "QuantityMin": 0
        }
      }
    ]
  }
}

PortalKey_Maze_Var1 is a real Icarus item, so $Requires: "Icarus:EchoOfIcarus" gates the whole patch: the bonus drop only appears when the Icarus pack is installed. The + appends; plain "Containers" would wipe the stock Rubble_Stone drop. See Replace vs append.

Case 2 - point a block at a brand-new droplist

First create the new list. This is a normal asset, not a patch (there is nothing to merge with). Write Server/Drops/Custom_Gravel_Drops.json with its own Container. Then patch the block to use it. The block file is Server/Item/Items/Soil/Gravel/Soil_Gravel_Sand.json, so the patch is Server/Item/Items/Soil/Gravel/Soil_Gravel_Sand.patch:

{
  "BlockType": {
    "Gathering": {
      "Breaking": {
        "DropList": "Custom_Gravel_Drops"
      }
    }
  }
}

Result

After

• Case 1: gravel still drops Rubble_Stone (1-2) AND now also rolls PortalKey_Maze_Var1, but only when icarus:legacy is present. The original entry survives because of the +.
• Case 2: breaking Soil_Gravel_Sand now rolls Custom_Gravel_Drops instead of its old Rubble_Sandstone list.