I mean... JetBrains IDEs have had this for more than a decade! When your cursor is on a variable, it highlights all of its other occurrences. It also highlight

I mean... JetBrains IDEs have had this for more than a decade! When your cursor is on a variable, it highlights all of its other occurrences. It also highlights shaded variables (in Go), private/exported functions, class members, package names, etc.