As the title suggests, a player owned notebook or clipboard (that can be stickied if need be). It has limited characters per page, but unlimited number of pages. Text input in game (similar to label maker, but accomodated to more characters), possibly saved to a text file that can be edited externally if need be. Text can be read from the pages directly (after input) and pages can flip with the same controls as other booklets. Must support basic text editor functions so you can format it a little and not have it just a wall of text. Text must also be deletable of course.
Would help in keeping track of different situations, train lengths, plans and order positions if using PersistentJobs, without using the external Dispatcher mod, and would fit neatly into the game. It can spawn at the tool shed/player inventory upon game start.