Since Jakarta, the sys_dictionary.attributes field max_length was increased from 255 to 1000 to accommodate longer strings of attribute name/value pairs.
However, the sys_dictionary_override.attributes was not increased to match, so it is possible that attributes on a base table's field cannot be be correctly overridden on a child table if the desired value is longer than 255 characters.
After carefully considering the severity and frequency of the issue, and the cost and risk of attempting a fix, it has been decided to not address this issue in any current or near future releases. We do not make this decision lightly, and we apologize for any inconvenience.
Note that while the sys_dictionary_override.attributes field's length can be directly modified by an admin user on an instance, if the modification is captured in an Update Set and then committed on another instance the modification to the backend table will be rejected. The [sys_dictionary] record will be updated with the new maximum length but the field on the underlying database table will not be modified to match.
Please contact ServiceNow Technical Support to discuss this issue if you are being impacted and need assistance to apply the necessary change.