Hello.
Above code looks correct. At least to show property in editor.
I’m guessing you might’ve forgot about setting your HUD class as default one in game mode/world settings?
See Game Mode and World Settings documentations for more info.
If you’d want to modify it in editor you’d have to use EditDefaultsOnly instead of VisibleAnywhere or BlueprintReadWrite instead of BlueprintReadOnly in UPROPERTY macro. First will allow you to modify it in default blueprint class, the second allows to modify it on runtime instance of your HUD.
As for this property not showing up in editor,