This is a lightweight plugin that loads all of the custom dimensions defined via datapacks as separate worlds. It only supports 1.16.4 and 1.16.5. You can also download a 1.16.3 version here.

Usage:
- Create a backup of your server, just in case
- Install plugin
- Put the datapack that has the dimension in your default world's datapacks folder (for example world/datapacks)
- Remove/rename any worlds that have the same name as a custom dimension
- Start the server

If you already have a dimension save from vanilla, copy the folders from worldfolder/dimensions/minecraft/<dimensionName>/ to serverfolder/<dimensionName>/custom/ although I haven't tested this.

Notes:

• The plugin saves world data in a separate folder, meaning you won't lose any data if you load the world without the plugin (or if the plugin crashes).
• If you use a world manager that's not Multiverse or Hyperverse and this plugin loads after that plugin, then it may not work properly.
• Dimensions with custom namespaces are supported, the world name is always the key by default (so custom1:custom2 becomes a world named custom2).

Configuration:
You can ignore certain dimensions in the config or you can change how a custom dimension is known to Bukkit. With the config below it ignores dimensions like minecraft:single_biome (or anything:single_biome) and loads dimension:name with this same name for Minecraft (so /execute in dimension:name works) but it adds the world to Bukkit as bukkit_name, all plugins will see it as such and it will have a folder named bukkit_name.