The Change Management System tab allows association of the application with any Change Management Instance which was configured in the topology. You must create the instance prior to configuring your application. Open an application, click on the Change Management System tab, and select a Change Management System Instance from the drop down to associate it to the projectapplication.
.
By default, the application configuration inherits the global Change Management System settings defined on the Administration -> Change Management Systems menu. It also overrides any settings defined by the parent folders up the chain.
...
The Default tab provides configuration for the Application scope, meaning it applies to all deployments for this project across all environments. When configuring at the Application scope, the setting apply to the applications and any of its projects (unless overridden by another project).
...