Hello, I’m a 17 year old with add and while I can’t say for certain what I do will work for your son it might be worth a try. I used to have the exact same issue. I stopped using draws because not being able to see everything or shuffle through was difficult so I always ended up getting it all over the place. I now hang all of my cloth I can and have a hanging basket for all other stuff.
You can also try if you haven’t already slowing showing him how to clean certain things around the house step by step to get him to learn to do it was he becomes idle. My parents had me doing chores so that I learn to just sweep or wipe stuff off when I get antsy. Once I got used to things being clean It would start bothering me if it wasn’t.
While I still have some struggles with my room I now keep it in good shape.
Also try saying he has to be able to see most of his floor before getting to do other things so that he will get in the habit of having it cleared.
Now most of this won’t help a lot in the short term due to most of it being habit. It can help with long term coping. Add does not always get better with time so it is very important to set good habits early. It really made a world of difference for me. I really hope this helps. Best of luck.
Oh one more thing that I think is very important but may be differ person to person. Try having him come up with the organisation. I can never keep things were they go when someone else decides for me, but when I decide it is much easier. Tho many people are the opposite and need to have it decided for them.