this is sort of what modern ides (e.g. jetbrains stuff) already do in the bg. when im working on stuff, i almost never navigate via text or the file explorer, i use things like "goto usages or definition" and navigate via what is essentially data tracing. this only works well with statically typed languages ime, though.
the indexing step is basically building this db in the background, it's just kept out of view / hidden unless you're building ide plugins or whatever.
Value tracing is at runtime. JetBrains cannot trace how values flow through your code.
To do this, you need to instrument all your code, and track all the transformations that occur for each value. It's really difficult to do if the language is not designed for it and there are a lot of performance implications.
If your code is written in a functional paradigm it becomes much easier to trace...such as with rxjs.
At this point I'd settle for making the background DB a read/write interface to the codebase. Value tracing is nice, but there are many, many lower-hanging fruits that would improve the coding experience by orders of magniutde, and that can all be handled statically, or without global code instrumentation.
the indexing step is basically building this db in the background, it's just kept out of view / hidden unless you're building ide plugins or whatever.