Asset search function fields when entering SR

We are using barcode ids with 7 charachters for assets, and we differ from this number. However when entering a new SR we try to search for the asset barcode (which is a custom field) but the search function does not work for that field?

the asset search page is this and we can only search in; 7 fields like name, type, description ...

How can i achieve searching for the custom field when creating SR?