What you're describing is generally known as interprocedural dataflow analysis. (Interprocedural because it handles dataflow across function calls.) You can lo

What you're describing is generally known as interprocedural dataflow analysis. (Interprocedural because it handles dataflow across function calls.) You can look into building a tool that can extract all or at least part of that dataflow graph for you by analyzing the AST. There are different approaches to this, some being more imperative (write a program to implement a chaotic iteration algorithm which builds the graph) and some being more declarative (extract facts about the code and feed them to a Datalog engine alongside a DL program describing the relations required to build the graph, or utilize something like CodeQL which already has the functionality available.)