Okay so this is a biiiiiiiig question and is probably why I haven’t tried to answer this until now. 
How would you design a JD system for all of Apple? I’d start by working for Apple and understanding their business.
And then I probably wouldn’t recommend a single JD system for it. And if I did, I’d probably spend about a year and charge them something like $2m to do it.
So if you work for Apple, drop me an email and we can talk money.
See the post ‘My personal system’ or browse the many other topics here where people have discussed their own.
But the short answer is: it depends. I can’t tell you what areas you have in your life. What hobbies do you have? Do you have a family?
The guidance on the website is to ‘write everything that you do on a sticky note’ and then to ‘group them together in to categories first, and then group those categories in to areas’. I wrote that five years ago, and it’s still what I’d recommend today.
The thing here is that you’ve already got a system with 7 levels of hierarchy, as far as I can count. Now that’s not to say that this is a problem — does the structure you’ve shown us not work? If it does work, don’t try to change it just because my website says you should.
My system works if you have a bunch of stuff that isn’t already organised in a neat hierarchy. It gives some guidance about how you might do that. But what you’ve got there has a hierarchy built in. Use it!