Hi JK,
You can achieve by 2 ways, One is just creating a display field in result view and have to code in GET method of the new attribute. This will display not have any relation with BOL entity.
Another way is you can enhance the result entity bol structure and have to code in a enhancement spot. This way you can use the field wherever you are executing the query object.
You have to create enhancement CRM_BADI_RF_Q1O_READ, for more details refer below link
Search Result Enhancement with custom z fields
Best Regards,
Dharmakasi.