How to make the world deeper

Yes it is possible, it cannot be done with MCreator but with a little coding the height and depth can be expanded. Also the ratio of stone and deepslate can be manipulated too. It only works for 1.17 and newer (1.17, 1.18, and 1.19 can be manipulated with simple *.json files for world generation).

I did it on Unexpected Jaunt and Shattered world limits, both mods are created with MCreator. If you find them on Curseforge, there is also a 1.19 version ... but that I coded manually. Every version need a different format, the following is for 1.18.2. If you have some coding understanding, look at the data folder inside Shattered World Limits mod in ...

data\minecraft\dimension_type\overworld.json  (change lines 2, 8, and 9)

{
  "logical_height": 1152,//TOTAL HEIGHT
  "infiniburn": "#minecraft:infiniburn_overworld",
  "effects": "minecraft:overworld",
  "ambient_light": 0.0,
  "respawn_anchor_works": false,
  "has_raids": true,
  "min_y": -128,//TOTAL DEPTH - better if in increments -64, -128, -256, etc.
  "height": 1152,//TOTAL HEIGHT - must be same as logical_height - for a total of 1023 high
  "natural": true,
  "coordinate_scale": 1.0,
  "piglin_safe": false,
  "bed_works": true,
  "has_skylight": true,
  "has_ceiling": false,
  "ultrawarm": false
}

Anything after // will be ignored by the game.

Also you will need to change the values in   data\minecraft\worldgen\noise_settings\overworld.json   to match the previously provided settings.

This part is way longer, so open the file in your code editor and look for line #4973 and change the values to match the previous given. I know I wrote it twice, but if not done like this the world will not generate.

    "min_y": -128,//SAME AS LINE #8 OF PREVIOUS FILE
    "height": 1152//SAME AS LINE #9 OF PREVIOUS FILE
  },

For the deepslate stay in the same file  data\minecraft\worldgen\noise_settings\overworld.json and go to line #2303, you will see the following ...

        "if_true": {
          "random_name": "minecraft:deepslate",
          "true_at_and_below": {
            "absolute": 0//THIS VALUE HAS TO BE CLOSE BUT LOWER THAN THE VALUE BELOW
          },
          "false_at_and_above": {
            "absolute": 8//THIS VALUE HAS TO BE CLOSE BUT HIGHER THAN THE VALUE ABOVE
          },

Mostly nobody will explain this, it has several hundred thousand lines in total (depending on what you are trying to create/change). At first it might look like a lot and sort-of scary, but you are only changing 7 values for now.

One step at a time.

Yes, you can use the code in my mod or get a template at ... https://misode.github.io/worldgen/

If you like, change the title to [TUTORIAL]

Which json file are you working on?

In this scenario you will need two json files. Both are named the same, but with different content and location.

• one in data\minecraft\dimension_type\overworld.json (this is the shortest file)
• one in data\minecraft\worldgen\noise_settings\overworld.json (this is the longest file)

These files work together, in other words ... they need eachother in order to work correctly. Both files are named overworld because they are for the Overword (dimension where you spawn in Minecraft). For custom dimensions it will require similar, but more advanced coding.

In order to help you better ... you will need to be very specific, worldgen is not difficult. But the more specific this conversation goes, the better you will understand what you are trying to do and/or will do in future modifications.

How do I change it for other vanilla dimensions?