Create reason codes
Dynamics 365 for Finance and Operations has evolved into purpose-built applications to help you manage specific business functions. For more information about these changes, see Dynamics 365 Licensing Guide.
Click Service management > Setup > Service orders > Stage reason codes.
Press CTRL+N to create a new reason code.
Press CTRL+S to save the reason code.
When you are prompted for a reason code to explain why you are updating a stage of the service order, you can select any of the reason codes that you create here.