There is a setting in the Blueprint Editor Preferences - Hide Construction Script Components in Details View - which will show these kind of dynamically created components in the Details View if it is unchecked.
When a custom component is added at runtime, it does not show up in the details panel when you select the blueprint that it has been added to.
Found in 4.9.2 binary. Reproduced in 4.10 Preview 3 and Main CL 2749677. Also reproduced in 4.8.3 binary.
1. Open the editor
2. Create a new blueprint based on Actor, and another based on Actor Component
3. On event begin play, add the actor component to the actor blueprint
4. Place an instance of the Actor BP in the level.
5. PIE
Result: Checking the actor bp's details panel displays no component, even though it has been added.
Expected: The Actor Component BP would be displayed under the Scene Root of the Actor BP.
Head over to the existing Questions & Answers thread and let us know what's up.