How to create a new Wall Item?
The best way is to Duplicate an existing wall item in the DataGoup Catalog and then modify as needed :
1) Open Catalog Editor:
3) Name the duplicated Item accordingly and set the property values as needed:
NOTE: Is it usually preferable to create a new XML in which to store your custom catalog items:
4) Now you will see the new Wall catalog item in the DataGroup Catalog Editor and available for placement in the Place Wall tool: