I think also UGameInstanceSubsystem with an ActorComponent.
Subsystem and actor components talk and do registeration, unregistration.
UMG talks with subsystem and updates lists with events and actor references.
When item is clicked Actors Component is retrieved which holds data, and in umg is displayed. Visual feedback happens like overlay material to component owners static mesh if any. Better to send clicked function over subsystem to actor so UMG becomes independent fully from system itself.
When data edited Actors Component data is written.
Actors component save its own data as SaveGame object on event or endplay, retrieved in begin play if exists, if not displays default.