Sometimes when adding instances to Instanced Static Mesh component, you can click on individual instances in the editor and get special detail view - simple transform with the instance index number in the name and a button to promote the selected instance to an actor. You cannot access any other information about this selected instance in the editor, and Selected actors node returns nothing.
When you create another blueprint (using same class - Editor Utility Actor), although the process of creating instances is the same, you cannot access individual instances anymore. The second blueprint only allows us a selection of the whole blueprint with all instances selected (outlined).
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-187326 in the post.