RCM now allows you to search for additional drivers on the Reservation Enquiry and Update Report.
In this report, that is accessed by going to Reservations >> Reservation Enquiry and Update, you can search for a customer based on their Last Name, Email address, Phone/Mobile number, Membership number and Passport number. When you search for these, the report will return all booking with this value reported against them, whether it is for a primary or additional driver.
Additional driver will be marked by an "extra" label next to their name, as shown below.