Selecting a blueprint with a camera in it will allow you to preview the camera, but if your blueprint has more than one camera you can only preview the highest one in its heirarchy.
With the ability to view and select components from a BP's details, it would be expected that selecting different cameras inside the BP would change the camera preview.
Would also be expected that you can pin multiple camera previews from one BP.
1. Launch a Third Person BP project
2. Find the ThirdPersonCharacter blueprint and open it
3. In the components editor, add a camera component
4. Compile and close the BP Editor
5. In the default level, select the ThirdPersonCharacter BP instance
6. In the details panel, click on the different camera components
Result: The camera preview in the viewport stays on the highest camera in the hierarchy
Head over to the existing Questions & Answers thread and let us know what's up.