Chris.
Surely pencil items are only available to the Admin team!
Clearly I misunderstood the original enquiry.
Aircraft codes are entered under the "Alternative Code/Name:" heading in the "Aircraft" section of the profile. All the various codes in an airframe's life are entered in this section without raising a new profile, including any name given to the aircraft.
Unfortunately "Alternative Code/Name:" is not included under the heading "Correct or submit additional aircraft data" on the profile stage and therefore I suggest that changes and additions to this section are requested using the the "Comment on this aircraft" which is also on the profile page.
Or to put it more succinctly, submit a Comment describing the code addition and Admin will make the change.
Malcolm.