This is generally called Occlusion Culling and it is in UE4, although it doesn’t unload the object from memory (cause it may come back in view).
Here is basic information on how UE4 handles it, and basic debugging occluded objects.
Are you looking to destroy/garbage collect any objects that go off screen? Kind of like tappy chicken (Where things come into view, but onces they leave it doesn’t matter cause it should never come back?)