To me, the closest to a mental model would be a combination of + domain model diagrams (illustrates domain objects and cardinality relationships) + sequence d

To me, the closest to a mental model would be a combination of + domain model diagrams (illustrates domain objects and cardinality relationships) + sequence diagrams (expressing flow in between systems) + state diagrams But what I found in the real world is not many people use these UML diagrams except in really large companies. I totally agree that the current ways of forming mental models (through watching tutorials, reading docs, writing code, and taking notes) is super painful.