Linking a Test Case to a Requirement using the TC number - Is this possible?

Hello, It would save me a lot of time if I could link a Test Case to a requirement using the TC number in 'Test Coverage -  Available Test Cases ' section rather than selecting down the list (this requires knowing where the Test Case has been saved in the Test List). It is possible to associate requirements or incidents using the RQ or IN number but I can't seem to find a quick way of linking tests to requirements. Also if the 'Available Test Cases' had a search field this would be very useful. 

Many thanks for your time