I think it would be handy to have an option for highlighting all occurences of a given variable within a context. For example, this would help you easily see every place a parameter is used within a function. VAX already has the "Find Next/Previous by Context", whereby you can jump to the next/previous occurence of a variable, so the backend work for this new feature is already there and it would simply need to be mapped to a hotkey to make it useful.