I wish something existed in this space. I used Coati Software's Sourcetrail for a couple of years. Unfortunately it was discontinued. It was a wonderful piece of software that indexed a code repository, and exposed an interface to explore it interactively. At least for me, it significantly improved the understanding and legibility of code.
I'm still using Sourcetrail daily for inspecting C++ codebases. Works great. I paid for the first beta and was very sad that the company was not profitable. It really is a great product.
The code is in an archived state (https://github.com/CoatiSoftware/Sourcetrail). Searching for the software on Google shows some screenshots.