https://docs.unrealengine.com/latest/INT/Engine/UMG/QuickStart/3/index.html
3. Creating a Main Menu
- Select the first Vertical Box and in the Details panel, rename it to MainMenu, check the isVariable option and set ZOrder to 1.
A step is missing after step 6.
A step needs to be added to select the second Vertical Box and in the Details panel, rename it to OptionsMenu, check the isVariable option and set ZOrder to (?).