You can’t since C++ created Enumerators do not generate a blueprint class (the BlueprintType identifier is only to reflect them and allow them to be used in blueprints). Reference viewer can only show you blueprint class based objects.
I’m not quite sure however how you would go about finding every place you have used the class, since whenever making an enumerator visible in blueprints its simply to get it as a return value or something like thant and not to create variables of it in blueprints.
I’m leaving this as a comment since I know it does not fully answer your question. Have a nice day.