Some gizmos/icons to preview where some invisible objects are in the editors will speed up the process a lot. Items like:

• Cameras
• Directional Light
• Point Light

Also, it's a little bit hard to see the directional light "direction", since there is no shadows, so an icon will speedup the process. An idea for the directional light is add this dot present in Blender 2.8 that the user can groab it and draw thought the scene to aim the light at:

Unreal Engine 4 have some very intersting gizmos for these objects:

The camera preview on the bottom right helps a lot as well.