hi 
Ashley !
I made a mockup for scene graph
Scene graph in the Project Bar
in the "Project" bar there is new folder with name "Scene"
How will add new scene
when we right-click over "Scene" there will be option to "Add scene". On "Add scene" clicked a popup will appear similar to family popup (Image-4)
After selecting images and close popup. Our "Project" bar will look like Image-3 (left side) and all the images we added in character scene will look like a single image in layout (Image-5)
Assign Object as Child
On double click "Character" scene in the "Project" bar OR double click any image in the layout will open "Scene Editor" (Image-2) and then we can assign objects as a child or parent by dragging objects in the "Project" bar OR by dragging any image in the "Scene Editor". In the "Scene Editor" click any image and drag and then move it over the other image and drop there. it. will make dropped image as child object. After assign object a child "Project" bar will look like Image-3 (right side).
After assigning objects double click anywhere in the "Scene Editor" to exit "scene editor"