How pull the attributes from the Goal Definitions and Goal Progress and display in Notification?

Summary:

Need to customize notification "PerformanceGoalRespApprovalNotificationReport" to include fields from Goal Definition and Goal Progress

Content (please ensure you mask any confidential information):

We expected to customize the notification that a manager receives from an employee 
regarding goal updates. We wanted the notification to display some fields from the Goal 
Definition and Goal Progress. However, after reviewing the options, we found that not all 
fields are available to be displayed in the notification. We just could show in the notification the (flexfields)

Required fields                       Available?     
Goal Name                              Y
Goal Description                    N
Comments                              N
Start Date                               N
Target Completion date       N