You may refer to the similar article at http://support.qne.com.my/article/3203/58506
All the user defined field should be add in the current objects "BOModel". and All the common table name may request to add the user define field from the object start with "QnEBS.BO.XXX" which XXX usually represent the name of the module. in this case, creditor/supplier module will be refer to "AP"
1. Please go to Tools>Customization Centre
2. Select BOModel and navigate and look for an object name "QnEBS.BO.AP"
3. Navigate and select "Creditors"
4. Select "Own Members", Own Members refer to the unqiue fields in this table
5. Right Click and select Add>Persisent
6. For details, you have to visit http://support.qne.com.my/article/3203/58506 to learn more.