Seems tagging something EditorOnly still loads it when running in the game view of the editor. Is there something similar that will only show objects in the scene view while editing, and not load them when running, editor or otherwise?
I realize I can just tag these things, or look for EditorOnly myself and destroy them. But it would be nice not to and I thought this might already be in place.
Answering your main topic question, “only show an object in the scene view” what I do is create a new rendering Layer, call it “Guides” or “No Render”… whatever. Set the objects you do not want rendering in your game view to this layer. Then in your camera’s Culling Mask options, uncheck that layer so it won’t render it.
There you go. You will see those objects in Scene, but not in Game.
As for not loading or including in your builds, the Tag “EditorOnly” should not be including inactive objects and their dependencies (Unity 5.0)