Extra fiddlin' and I managed to find it. Now.. the box and the safe... :)
Viewing post in New puzzles
We will make this more clear in our next update, as many didnt seem to find the connection there.
In the shelf with the books there is a picture on the wall which shows different medical items of different height. You must adjust the books with the right topic on that height and then put the symbols in order of the items on the picture from top to down at the safe.