the various planes.

This one is kind of a unique one.

Why are there no such sections for off earthland threads? We've seen people go through dimensions and go places such as Edolas and also the Celestial spirit world and perhaps there are even more planes that just haven't been discovered yet such as heaven and hell or even a dream world or personal dimension created by a characters magic.

I suggest making a general section for "outer planes" where threads that can't fall into any of the locations and categories placed can be held. They'll be responsible for providing a means into the plane they've created and describing it once they get there(as there is no reference to go off of). I'm not saying let them create subsections in the section just let the section stand as is.

The main reason there are not sections for these seperate planes is that they are not able to be travelled to by conventional means.

i.e. edolas can only be accessed through anima. We also only really use it for events
celestial spirit world can only be accessed by holding onto a key and without celestial spirit clothing you will not survive there
heaven and hell are not really defined things, but we have had people travel to them. It might be possible to add sections for travelling to realms of the gods and realms of demons...maybe

I guess that's kind of the point of making a single vague section for it rather than individual sections.

They're hard to get to, but if your character wants to access these areas and finds a way to access them, there should be somewhere to put the thread so it doesn't feel way out of place. Just have a single section make the conglomerates of everything. Your right that it won't be used much but the option to go beyond what's given is something for people to look at. Everyone will interpret things slightly differently for their stories needs and wants so giving them control of the scenery gives them that option. The only thing staff would ever need to keep an eye on is if they had a rational means of getting there.