I love this game, but there is a major issue with 100% completing the game that was present in Psychonauts 1: trying to find collectables you are missing. If you are missing a single fragment, bag tag, etc., it could take hours combing through the whole stage for a single fragment. And when doing this, you'll most likely be looking through areas you have already completed, which is wasting your time. This is very frustrating, not fun at all, and makes 100% completing the game more of a chore than a challenge. You could look up a list of every collectable to find where that one last collectable is, but that takes all the challenge away.

A solution I thought of is to show where collectables are when selecting a place to teleport with the little green bubble blower thing. It would display what the player is missing from an area and what areas they have completed. I have made a mock-up of what this might look like to better explain how it would work. By implementing this, it would help the player find what they're missing more easily while still leaving the challenge of finding it.

I have an alternate solution that could work as well. Otto Mentallis's Thought Tuner doesn't work in brains, but maybe it could get an upgrade or just a new gadget entirely designed to locate collectables you are missing while in the minds. This upgrade/new gadget should probably be unlocked after beating the game. It could also have a longer range, and customizability to what you are looking for (figments, nuggets, etc.), being similar to Breath of the Wild's searching system. This would probably be harder to implement than the other solution though.

Either of these changes would make completing the game easier and less frustrating of an experience. But if you do implement these, try to make them optional for people who want to don't want to use these.