When Auto-numbering is enabled for the Action Item object, auto-number is populated into the Action Item Subject (name) field. It does not use an ID or CODE field. Why is this different from the way that auto-numbering works on other objects?
As you have indicated, the use of Auto-Numbering on the Action Item Object does not work like other objects.
Since the Action Item Object does not have an out-of-box 'Action Item Code' attribute, the system is populating the Action Item Subject field with the auto-number value. The Action Item Subject field is not restricted and non-unique values can co-exist. If we manually create an Action Item with a Subject that may exactly match the value generated by the Auto-Numbering, the system does not indicate that a previous record already exists. Also, since the Subject field is now being used for the Action Item Auto-numbering, the end-user does not have this field available for entering a subject. This is the current design of the Action Item Object and how it behaves.
If you want to use Auto-numbering in the Action Item Object you can use the following steps to create your own custom attribute and turn on the auto-number on that attribute:
1. Administration, Studio: Objects, Action Item, Attributes tab
2. Click 'New' Button
3. Create a new string attribute (you can give any name to the new attribute such as 'code' or 'ai_code')
4. Click 'Save' button
5. Go to the 'Auto-numbering' link on this attribute
6. Define an auto-number scheme and activate the auto-numbering
Once you do this, you can update some views and portlets to reveal this custom attribute throughout the application.
You can update the Action Item Object Views:
1. Administration, Studio: Objects, Action Item, Views tab
2. Action Item Properties [Layout: Create] [Layout: Edit] - move the new attribute to the page layout
3. Action Item Details [Layout: Edit] - move the new attribute to the page layout
You won't be able to modify the configuration of the Action Items (calendar.myActionItems) portlet since this is a System-Restricted Portlet.
You won't be able to modify the Organizer: Action Items portlet as this portlet is not available for configuration.