Before custom attributes can be added to model elements in the properties dialogs, Custom Attribute Types must be defined for the model element type. Custom attribute types are model-specific. Custom attribute types can be created in the Modeling Options dialog, where the model element types are also defined for the current model.
When using the default template, the following model element types can be assigned custom attribute types: Process Step Types, Connector Types, Groups, Information Stores, Material Stores, Notes, Organization Items, Measures, Cases, Information Items (shown in picture below), and Resources.
From the Modeling Options dialog, you can define model element types by clicking the View... button for the desired element. In the Custom Attributes Tab for that selected model element you can add custom attribute types to the model element by clicking the Add... button.
If the Metamodeling Browsing feature has been enabled by your license, you can view the number of elements (of a particular type) having values for the attribute type and have more detailed usage information displayed by clicking the Information... button.
If you want to create new custom attribute types, in the Custom Attribute Types tab of the Modeling Options dialog, click the New... button to create a new custom attribute type.
For example, to define custom attribute types for the Information Items of the current model, open the Modeling Options from the Model tab of the ribbon, and on the lower part of the Model Elements page, click the View... button to the right of "Information Items". The Information Item dialog (shown below) opens. Now when creating a new information item in the model, you can assign values to the custom attribute of the information item.
Custom Attribute Types of the model's Information Items