Tried to make a skyblock world with only minecraft:the_void as biome. I've tried multiple inputs, but nothing seems to be working. Documentation is unhelpful.

"World": {

// A list of biomes for each dimension.
// You can not use this for the end dimension. The end dimension will always have it's five biomes.
// These are resource lists. See https://noeppi-noeppi.github.io/LibX/io/github/noeppi_noeppi/libx/util/ResourceList.html#use_resource_lists_in_configs
"biomes": {
  "minecraft:overworld": {
    "allow_list": true,
    "elements": ["biome":"minecraft:the_void"]
  },
  "minecraft:the_nether": {
    "allow_list": true,
    "elements": ["biome":"minecraft:the_void"]
  }
},

Ahh yes, it’s because the default world generation doesn’t have this biome. It removes each biome which isn’t in that list but it wouldn’t add if the list of all biomes is empty. This needs to be fixed!

This appears to still be an issue as of 1.18.2-3.3.31;
"biomes": { "minecraft:overworld": { "allow_list": true, "elements": [ "biome":"biomesinjars:dead_land" ] }, "minecraft:the_nether": { "allow_list": false, "elements": [] } },
didn't work, so I tried

`"biomes": {
  "minecraft:overworld": {
    "allow_list": true,
    "elements": [
      "biome":"minecraft:the_void"
    ]
  },
  "minecraft:the_nether": {
    "allow_list": false,
    "elements": []
  }
},` which is the same case that was being tested here, and the overworld still has all the biomes.

Remove "biome": and try again. If still not working, show me your log file, please.

OK, so the process here was to set the config, boot minecraft, create a new world to see if it has the biome, close minecraft, and copy the log file.

1. "elements":["biome":"minecraft:the_void"]
   Result: Starting biome is Taiga
   Log: https://gist.github.com/Flabort/760be069c0081e386b49d792dad06649

2. "elements":["minecraft:the_void"]
   Result: Partial Success? I don't know why it worked this time, and not before I added, and then subsequently deleted "biome":, but starting biome is The Void; Still, this test case tells me your code worked for the vanilla biome, I'm still trying to get a non-vanilla biome to work.
   Log: https://gist.github.com/Flabort/0cbe49bf64c3677dc68f5e6c4545a1b8

3. "elements":["biomesinjars:dead_lands"]
   Result: Starting biome is Forest, realized I made a typo https://imgur.com/OD2b5Fb
   Log: https://gist.github.com/Flabort/aa05fb9401b69c656e02f4f2e75805f8

4. "elements":["biomesinjars:dead_land"]
   Result: Starting biome is Ocean, so failure to make the world a modded biome
   Log: https://gist.github.com/Flabort/1be99c9187277a146040e368ebf33502