To use the custom dimension effect, create a standard dimension and set the effects in your dimension type file to:

"effects": "corewithstuff:space_effects" Dimensions that use this effects will not have world border.

What this does

This setting essentially turns your dimension into a void by disabling the following features:

To register a planet, you need to create a JSON file at data/corewithstuff/cws_planets/planetname.json