I try to create a little booklet with formulas that I need for university. Since we are allowed to use formularies (I'm not shure, if this is the right word for that!) in exams, it's absolutely crucial to find each formula as fast as possible.
Therefore I try to create a register at the page margin like on phonebooks or addressbooks as seen in the picture below. (What I would like to generate are those red letters. But preferably not only one letter but a few words)
Thanks in advance!