Scene composer - blank screen - newbie to jme3

I selected a scene (j3o object), saw some orthogonal arrows on a black background, turned the mouse wheel and the arrows shrunk out of site. I can’t get back to seeing the window contents. How do I rescale/reset/recenter the view in scene editor?

It may be that your model uses the lighting material and that you have no light in your scene.
You can click on the little light bulb at the top left corner in the toolbar of the scene composer.