Make both the label and the code from the controlled vocabulary registry searchable
When adding a controlled vocabulary to the registry and afterwards connecting it to a certain MARC field in Primo VE, patrons now can only search using the code and not the label.
As an example imagine a controlled vocabulary with the entry ECON (code) and Economy and Finance (label). If ECON (the code) is stored in the record and the patron searches for Economy and Finance in that field (in advanced filter), he or she will get no results. If you search for ECON however all relevant records will be returned.
Of course the patrons are not supposed to know these codes, thus rendering the use of controlled vocabularies in search scopes practically useless.