Create the screen through the assets menu

Create -> UI.Windows -> Create Screen 

Create new layout through the screen's component Layouts tab

Create new scene. Put there prefabs:

• WindowSystem prefab
• Created screen prefab
  • Created layout prefab

Now you can build screen according to preferable design

For example: I put 2 WindowLayoutElement blocks into the TestLayout/Element

Then I created inner components and stored them as prefabs

Now I can save layout/screen prefabs changes ignoring components using ✅Apply UI.Windows button:

• If you use ✅Apply UI.Windows on the screen prefab (derived from LayoutWindowType), screen prefab will be applied ignoring inner layout

• If you use ✅Apply UI.Windows on the layout prefab (WindowLayout type), layout prefab will be applied ignoring inner components (derived from WindowComponent but excluding WindowLayoutElement components)

• Button ❌Revert UI.Windows works in the similar way - it reverts prefab's changes, but DON'T remove spawned inner components

Summary

• You can edit each screen on it's own scene
• You can apply (or revert) screen/layout prefab changes ignoring inner components
• You can quickly return back to the screen editing as it's stored in the built state on the editing scene
  • Each time you apply screen/layout prefabs, they are stored without any components garbage