You want to create an absence type that can be entered only by administrators.

Use the Eligibility Profiles on the Absence Plan, to set the participation rules.

On the Absence Type, enable administrative updates only within the display settings, add two plans in the appropriate order of priority, add reason values, and select "Display and edit" for the Reason field for administrator within the display settings.

Create a separate absence framework (Plans. Types. Reasons, and so on) for Administrator usage.

Use security profiles to establish who can add and update specific absence types and reasons.