I'll always have a soft spot for Racket, because of how the IDE literally draws arrows for you, overlaid on top of the code, linking the various occurrences of a (hovered) variable together.[1][2] Seriously, how cool is that? Alas, it's unclear how to begin to implement such a feature in a performant way in a DOM-based editor like vscode (I'm not a web developer, so maybe I'm wrong about this.)
[2] > Lexical Structure: The lexical structure is shown with arrows overlaid on the program text. When the mouse cursor passes over a variable, DrRacket draws an arrow from the binding location to the variable, or from the binding location to every bound occurrence of the variable.
[1] Example gif: https://docs.racket-lang.org/define-attributes/examplecodear...
[2] > Lexical Structure: The lexical structure is shown with arrows overlaid on the program text. When the mouse cursor passes over a variable, DrRacket draws an arrow from the binding location to the variable, or from the binding location to every bound occurrence of the variable.