Would a question on writing an outline specifically for my worldbuilding belong in the Worldbuilding Stack Exchange or on the Writing Stack Exchange? I mean general advice for how to structure my outline and how to address things from culture, geography, economics, and living needs to things like fictional classification, magic systems, technological developments, and genetic engineering? I get that plot and character building would be better suited to the Writing.SE, but for my worldbuilding I'm not sure.
general advice for how to structure my outline and how to address things from culture, geography, economics, and living needs to things like fictional classification, magic systems, technological developments, and genetic engineering
This would probably be closed as Too Broad or Primarily Opinion Based on both sites, sorry. Stack Exchange, as a whole, is about specific questions with specific answers that can be objectively judged good or bad. If you have specific question in mind, it might be a good fit here, under worldbuilding-process. If in doubt, post it in the Sandbox first, and people will tell you if there are issues with it, or if it is potentially a good fit for this site.
Depending on the way you phrase this question it might very well be on-topic on both sites.
To post on WorldBuilding you have to make sure that you show why you want answers from a WorldBuilding perspective. We try to give the author the benefit of doubt - if they post on WorldBuilding instead of Writing they likely want a WorldBuilding perspective - but it's important to communicate clearly what you are hoping to get the kind of answers that you are searching for.
Here on WorldBuilding we have some tags that categorize questions that go in a similar direction and might give you some ideas on how you could phrase such a question. For example you can look at the tag worldbuilding-resources to get an idea of how questions should be framed that are searching for resources that can aid you in building your world. This might be useful if you want to see examples of a structure.
You should also have a look at the questions in the tag worldbuilding-process, which is used for questions that are asking for the general steps that are required to do something. If you prefer to get a rough step-by-step answer that helps you create your own structure this might be helpful for you.
There's also the tag software-recommendations that is used for questions that ask about software that can help you in creating your world. For example the question What software is available for keeping and organising notes about your world? might be interesting for you as the software already gives some information about how to structure your worldbuilding stuff.
In any case: I recommend checking out our Sandbox where we can help you with the phrasing and tags once you have a draft ready.
If you are interested in a writing perspective Writing.SE might be better. Their focus would be more generic on the "How do you keep your notes?" front, but you should check out their tags, too. For example they have a world building tag and a software tag, which might be useful to you.