As you mentioned, if the dragon is in the scene it will be loaded.
However, to solve your problem of wanting to see your setup. You could create an empty game object (placeholder) to replace the dragon and have a script which an AssetReference which would load the dragon before it would be visible to the player, and unloads it after it is defeated or the player is to far (basically when it is no longer needed.)
In the editor you can also use either OnDrawGizmo to show the dragon when the GameObject is selected or actually load the dragon as a child of the placeholder GameObject with the dontsave and hide flags in an editor in an editor only awake method. (Do destroy it in the OnDestroy method)
thank you knowing it will be loaded helps me understand it. Iām using addressable for some text files that load, so I can keep my eye out now for other assets that live outside my scene.
yeah this setup presents challenges for those of us working heavily with scene views. I have to edit the dragon a lot in place. But I didnt know you could draw a gizmo using a mesh and that is cool.
I think a really helpful thing unity could do is add a check box that does kind of what you suggest making an addressable game object in scene automatically unload when you build it and show up in editor only just for editing and placement purposes.