I have grappled with this too sometimes. Feeling like there’s too much of a jump from one level to the next. @johnnydecimal has written/vlogged (?) about how IDs have gradually increased in scope over the years. As @njmatch3 points out, all short trips are now inside one ID, whereas ten years ago Johnny might have recommended each of them being their own ID.
When you’re putting something somewhere, the less depth, the better. Then when you’re looking for something, if the categories and IDs are well-designed, you need surprisingly little specificity to know where to start searching. And then with full-text search and filtering you’ll find what you need pretty quickly. Even if searching for something still takes a little while, you know for sure that you’re looking in the right place which makes all the difference psychologically. The more options there are up front, which would be the case with another level, the more places something could be, which induces anxiety both when saving it and when looking for it.
(and I think most of us have way less stuff than we think, once it’s well ordered. So there won’t be that much to look through anyways).
I experimented with a more fluid type of ID hierarchy, where by using alternating numbers and letters you can nest new ‘sub’-things without breaking the order. But I concluded that it is more hassle and confusion than it’s worth. It’s possible to encode a hierarchy of knowledge with great precision, but for that information to be useful you have to use it with skill too and for 99% of things it’s just extra noise that distracts you.