You can set the CityEngine preferences by clicking Edit > Preferences in the main menu.
The Mouse preferences allow you to select specific mouse schemes. CityEngine defines mouse schemes for major 3D applications. The schemes are read-only, unless you select the Custom scheme, which allows you to define the mouse actions for 3D navigation and editing.
You can set Mouse preferences under Navigation Devices > Mouse.
Note:
On Linux platforms, it is recommended that you use the CityEngine Linux scheme. This scheme uses Ctrl as the default modifier key and does not interfere with window manager operations that commonly use the Alt modifier.