This tab is accessed through File | Preferences and then selecting the Visual Preferences sub-tab.

Icon size
Sets the size for the icons in the navigation pane between Small, Medium or Large.

Multiline Tabs: Default = Off.
In the details pane, for entry types with more than two tabs, Manager can either use icon next tabs buttons to scroll the tabs horizontally or arrange the tabs into multiple rows. This setting allows selection of which method Manager uses.