An IDE that provides a linear view of your code base. Follow code paths as though they were all inline, e.g. expand views of function/method internals inside the calling function, etc. No more changing files/modules.
it should be transparent once you flatten the db to file(s) and run normally, but for IDE would need to be aware of this db structure. maybe a VS code extension might work!
that is the dream...
They make IDEs for many languages but the indexability of languages varies a lot depending on (mostly) how strong their type system is and how easily parsed the code is. Check out their structured search feature for an example of how to do semantic queries over the indexed AST.