The Child Actor Component cannot be selected in the Blueprint Editor Viewport. Selecting the Child Actor Component in the Components tab is the only way to select the component.
Reproduced in 4.7.6, 4.8 Preview 4, and Main (//depot/UE4/Promotable-CL-2578133)
1. Open any project
2. Create a new Actor Blueprint
3. Add a Static Mesh Component
4. Assign a Static Mesh
5. Create another new Actor Blueprint
6. Add a Scene Component
7. Add a Child Actor Component
8. Assign the BP created in step one as the Child Actor Class
9. Select the Scene Component
10. In the Blueprint Editor's Viewport, select the Child Actor
The Child Actor Component cannot be selected in the Blueprint Editor Viewport.
The Child Actor Component can be selected in the Viewport as any other visible component would be.
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