DARQ: Complete Edition

In chapter 2, at the end where you place the T shaped lever into the slot and use it to stop the subway train so you can cross to the exit, before you leave use the wheel to the right and turn it so there is a wall instead of an opening next to you. Walk up the wall and across the ceiling to get to the journal.

If you are going back and collecting any journals you missed with chapter select, you do not have to finish the level to save it. You can immediately quit to the menu / choose a new chapter after picking it up.