Web Screen Painter (WSP) does not allow modifying the new columns that were published.
CA Service Desk 17.1 and higher
After a site-defined schema has been published, web screen painter will consider it as a standard schema and will not allow any changes to the columns. To verify,
This method can only be used to adjust the length of an existing CUSTOM field, one that was previously established using Web Screen Painter Schema Designer.
Due to the controls in place on the backend MDB database schema, adjusting the length of an OOB field is unsupported.