this is C++ related only.
If this property declaration is placed on any AActor class, it’s not visible in BP editor as it should be. This is not the case if the same declaration is used in UActorComponent class. The property is still visible and editable in this case.
Is this bug or intent?
The behavior when added to an actor is expected. The EditInstanceOnly specifier means that the property is only available for edit on individual instances of the actor. It would also make sense that adding the property to an actor component treats each component added to a blueprint as an “instance” of that component, which is why it does appear in the blueprint in this case. I’m not positive if this is accurate however, and have entered a bug report, UE-30735 to investigate the behavior.
Thank you for your explanation and investigation;) Jiri