My mistake: the game tells you to open the Book of Skills before it is actually unlocked. To open the book, you need to finish the tutorial room (the Storeroom) first. Thank you for your feedback!
Thanks for your playing time! Lufar wants you to learn Capacity first. Press T(or Caps Lock) to open the book of skills and learn it. And the door opens right away. His line should have said which skill and how. Im working for it and next update fixes this misunderstanding.
Insight: mode 1 (Right places) doesn't light up whole shelves. It works with the item in your hand: hold V, aim at a shelf, and the ghost of your item turns green if it belongs there and red if it doesn't. Free places and misplaced items are shown by mode 2 (Out of place), which you learn in the book. The skill description promises more than mode 1 does, so I'll fix that in the next update too.