Hud details not visible in inspector

FPS1HUD is the active hud in the project settings. When I click on the hud in the content browser then there are no details in the inspector showing up to edit. I have for example this property:
UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = “Widgets”)
TSubclassOf TestWidget;

But I can only set it during runtime (press shift+f1 and in the worldoutliner select the hud and change the property). But how do I do this at design time?

This is what I get during runtime (and what I need during designtime):

I solved it. It seems that when the hud is a c++ class, you need to create a blueprint and derive it from that c++ class and then doubleclick the blueprint and set it there.
Also make sure to add the blueprint to the game&map modes in the project settings instead of the c++ class.