Felipe -
With the current GA release of the sdgtw probe (v1.30), this is accomplished by updating the only_incident_number_in_alarm_field key to add only the incident ID to the desired custom field in the alarm from the probe's Raw Configure page in the setup section.
For more information, see the Configure General Properties section in sdgtw AC Configuration. For example, if you enter this key value as custom_3, then, only the incident ID will be displayed in the Custom 3 field in USM.
Default: Blank
Note: You must enter a different key value from the one that you have specified in the CA UIM Alarm Field for Incident ID and CA UIM Alarm Field for Launch in Context fields under the sdgtw node > Probe Configuration section of the probe's Configuration page launched from the Admin Console.
Hope this helps.
Thanks,
Kathy Maguire