Quick explanation: MyBaseWindow: Is a prefab with a VerticalLayoutGroup that contains: BackgroundImage, Title, Content, StatusBar MySpecificWindow: should inherit everything from MyBaseWindow and then add one more thing: Lets say a "ToolBar" that must go exactly between Title and Content. While creating MySpecificWindow and adding your ToolBar, to MyBaseWindow you will notice that you cannot add it at a specific place, only at the very end. Which will cause the ToolBar to be below the StatusBar. Possible Workaround Add an empty GameObject to MyBaseWindow Just for the sake of clarity you could name it "InsertPoint_BelowTitle" Save the prefab In MySpecificWindow you insert the ToolBar into the InserPoint_BelowTitle object. Define whatever insert-points you need. This is somewhat ugly, but it works. Initially it seems this problem would appear everywhere, but as it turns out it's actually pretty rare, and the workaround is not all that bad (for now). ====== Old Post: After seeing that the nested prefab system is out now I had to of course test it. And the primary use case for our game will be the UI. For everything else we have custom scripts that compose things at runtime. For the UI that's an exception because of course it is a massive advantage to have a "WYSIWYG"-style editor, instead of having make modifications, run the game, stop, ... Anyway, so I immediately ran into a limitation: It seems you can add something to a prefab, but you can't add it at a specific position in the hierarchy? How would I do the following then? Adding a new panel in the normal scene mode: Adding a panel in prefab mode: In this example MyWindow is a variant of Window. The "Window" (title text for it is "Base Window Prefab" in the scene view) defines the titlebar, content, and statusbar. MyWindow is supposed to have an additional "tool-bar" exactly between "Titlebar" and "Content", so the VerticalLayoutGroup on Window (and thus on MyWindow as well) will do the layout correctly. I don't want to make "insert-points" where derived prefabs can add their own stuff, because it is not predictable what should get added and where, or sometimes there would even be "collisions". Like what if one type of window has a sidebar (vertically), and the other has a toolbar (horizontally)... so defining empty GameObjects just as markers or containers to insert new elements is not viable. Am I doing it wrong? It seems like I can only add a new object at the last index and not somewhere inbetween. Is that completely impossible? Is it planned as a feature to allow inserting at any index?