Captain America: Civil War - 16 Things We Learned From The Directors' Commentary
13. The Red Book Was Almost Something A Lot Weirder
Key to Zemo's plan to take control of Bucky to gain revenge for the death of his family is the MacGuffin red ledger that contain details of the secret soviet super soldier programme (and Bucky's trigger words). But it almost wasn't included at all.
According to the writing team of Christopher Markus and Stephen McFeely, they "danced around" the idea of using something else more complex (and by the sound of it, an awful lot sillier)...
“There were many drafts where they were chasing something called The Mind Crown.”That would have been the device put on Bucky's head in The Winter Soldier and during the opening of Civil War, presumably meaning Zemo would have had to seek the giant contraption. That would have made his break-in to "steal" Bucky a hell of a lot more clunky.