Dimension Stack
Use vertical connecting portals to "stack" the dimensions.
You can see the "Dimension Stack" button when creating a new world.
If enabled, the bottom dimension will connect to the top dimension, creating a vertical world wrapping.
If enabled, the portals will change your gravity direction when you go through. It requires Gravity Changer mod.
If no dimension is flipped, this option will have no effect.
By clicking "Edit" you can edit the selected dimension entry's options:
This controls the generated portals' scale transformation. The generated connecting portal won't change the crossing entity's scale.
If you want that one block in nether corresponds to 8 blocks in overworld, set the overworld's scale to 8.
It's recommended to either (1) set the scale between overworld and nether to be 8 or (2) set the nether portal mode to be disabled. Because dimension stack does not interfere with how nether portals work, if dimension stack allows player to travel between overworld and nether with 1 by 1 space ratio, and nether portal allows travelling with 1 by 8 space ratio, then the player can easily reach the world border by using two travel methods alternately.
Controls the portals' rotating transformation. If enabled, makes the dimension looks "flipped". Does not change the gravity direction in that dimension (unless you enable gravity change option). If a flipped dimension connects to a non-flipped dimension, the connecting portal will have a 180 degrees rotation transformation along X axis.
Controls the portals' rotating transformation. Make the dimension looks rotated along Y axis.
Specify the bottom and top Y level of the portal. You can left these two empty by default.
If Bottom Y is left empty, it will use the dimension type's min_y property. If Top Y is left empty, it will use the dimension type's min_y + logical_height.
Specify a block that the bedrock will be replaced into. If empty, the bedrock will not be replaced.
This mod has command /portal dimension_stack (since MC 1.18) that allows re-configuring dimension stack after the world has been created.