Maybe it is like building a bridge. You build from both sides and hopefully meet up in the middle somewhere.
I think many of us start, almost intuitively, with both the 50k and the 0/10k levels simultaneously as two more or less independent things. We gradually break down the 50k to the 40k level, and simultaneously and independently generalize and group our 10k stuff on the 20k, 30k and 40k levels. And that's where we meet ourselves somewhere - hopefully in harmony.
I keep up to the 40k level in my app, but only as "headings" (using tags, projects, prefixes, whatever features are available). Other written info (reference type info) about these goals I keep in regular files.
I have not "formally" connected my 40k and 50k levels. I can tell that they appear to be in full harmony, but they are not clearly linked in a definable fashion. It is more like a spaghetti linkage - everything connects with everything, but I can see that they both fit on one plate and look tasty together. I actually feel no real need to connect them more clearly, but at the lower levels I definitely want to connect the levels, for example see which projects belong to which area or goal etc.