I am used to old-fashioned library practice, and in recording my books (5,000 out of 10,000+ so far) I would like to get rid of tabs etc I feel unnecessary, such as credits and characters, plot and notes, contents, and add things like condition and rare/antiquarian to the data entry front page. I find the manual too confusing. I’d even be prepared to pay someone to do the personalisation.
Assuming you are referring to the Edit Book screen: I am afraid that screen cannot be customized.
BTW: I am sorry to hear you find the manual confusing.