This is possibly not answering the question, but the CAA logbook (CAP 407) section (11) in the part 1 Instructions for use stated that P1 (U/S) co-pilot acting as pilot in command under the supervision of the pilot in command should record in the column headed Pilot in command (p1) under the column headed commander you enter the name of the flights commander the actual P1
Is this not possible with your new logbook ?