I actually had a similar idea today. Except that instead of having a picture automatically added after completing an assignment, it would allow you to write in your own journals. So my theory of it is, if you are pationate about potions, or charms or the like, you would be able to start a journal and title it however fits best. So if you wanted to write down your favorite charms and what they do, or if you wanted to write down successful potions you have created along with the recipes, you would be able to. Maybe having it be an Item in your chest, so you would have to purchase it, then you could write in it, and if you ever felt like you don't need it anymore or you have copied everything into another journal, you could gift it to someone, or throw it away, or possibly submit it to the library at Hogwarts or a shop that sells books for review, and possibly have your book of knowledge be sold or used as curriculum.
I actually had a similar idea today. Except that instead of having a picture automatically added after completing an assignment, it would allow you to write in your own journals. So my theory of it is, if you are pationate about potions, or charms or the like, you would be able to start a journal and title it however fits best. So if you wanted to write down your favorite charms and what they do, or if you wanted to write down successful potions you have created along with the recipes, you would be able to. Maybe having it be an Item in your chest, so you would have to purchase it, then you could write in it, and if you ever felt like you don't need it anymore or you have copied everything into another journal, you could gift it to someone, or throw it away, or possibly submit it to the library at Hogwarts or a shop that sells books for review, and possibly have your book of knowledge be sold or used as curriculum.