Report Editor - ToolBar - Layout
This group is present on all tabs of the report toolbar. It allows you to switch between preview, scripts and editor modes.
Note, that you can use keyboard shortcuts ⌘+1, ⌘+2 and ⌘+3 to switch between Editor/Scripts/Preview modes respectively.
Here you can choose the size of paper (A4, A3, … ) and its orientation (vertical or horizontal).
Here you can define how many columns to have on page.
Here you can turn on/off one of report regions. You can read details about each region here.