This mod adds three types of worlds that players can access by crafting the corresponding portals: Mining Portal, Void Portal and Garden Portal

Each crafted portal will - when first activated by right-clicking - create a new dimension and transport the player there.
At the location where the player arrives in the new dimension, a Return Portal is placed. Use this to get back.
Portal blocks can be picked up and moved, even to other dimensions. Return Portals can only be moved within the dimension they were generated.
Server OPs can right-click a new (not yet activated) portal while sneaking to forcibly link to an existing dimension, using a GUI. Linking from within a Utility Worlds dimension to the overworld (via GUI) should be used with caution. The created overworld portal can be in a bad location (coordinates can be specified in UW for 1.14.4+)

Note: For 1.16.5+ you will get warnings about experimental settings for custom worlds. You can use Shutup Experimental Settings! to get rid of it if you want.

Thanks to McJty and Hyperbox (Commoble) for making it possible to figure out dynamic dimension creation in 1.16.5+!

Common for all worlds

No weather.
Always noon (sun at zenith).

Mining World characteristics

Completely flat.
No caves, water or lava. Note that other mods may override this behavior, there is no attempt to prevent this.
Flat bedrock.
Ore generation and mob spawning as in Extreme Hills / Mountains / Windswept Hills.

Void World characteristics

Black sky. star brightness is configurable, default is no stars (only in UW for MC 1.12.2).
Considered a plains biome.
No structures.
9 x 9 stone platform where the Return Portal is created.

Garden World characteristics

Completely flat.
Only consists of 4 layers of dirt on bedrock.
No ore generation.
No mob spawning.

Utility Worlds