UE 5.4 Change Inheritance in your C++ class to e.g. AActor, Update Project via Live Coding Patch, then set back to the class you want: The Component should during this process disappear, and pop back, forcing a refresh of the UI along with the Component viewer, so the viewer should work again (unless it wasnt working elsewhere too).
E.g.
class WHATEVER_API AMyClass : public AMyParentClass
to
class WHATEVER_API AMyClass : public AActor.
Then run Live Coding Patch. Then set back to:
class WHATEVER_API AMyClass : public AMyParentClass.
With this, the component inherited by AMyParentClass should be editable in the viewer.
This still requires to have set the UPROPERTY options correctly (which I assume you have checked already).