This functionality is new as of version 4.0.
In order for an Alert Type to appear in the 'Alert Type' drop-down list on the 'Add Inventory Transfer Comment / Alert' dialog, it must include the 'Inventory Transfer' Alert Category.
Refer to Configure Purchase Order Alert Types.
To Add Comments and/or Alerts to a Purchase Order:
Navigate to the 'Purchase Order Details' screen → 'Purchase Order Log' tab.
Click the ‘Add’ button.
Type the Comment/Alert text in the 'Comment' field.
Select the 'Alert' checkbox to create an Alert.
Select an Alert Type from the 'Alert Type' dropdown list.
Refer to Configure Purchase Order Alert Types.
The alerts that are created on this tab are ‘Purchase Order Alerts’, which will appear on screens that display Purchase Order Alerts.