First off, I'm still exploring the game and learning stuff, so plz be patient if you've heard this tip before.
I have found that when I run out of storage, I can still keep track of all my stuff by piling all of it into one pile against a wall. You may be wondering how I could possibly keep track of anything if everything is in one jumbled up mess. Well, I accidentally discovered that if I press the up arrow while my character is smack up against the wall where the stuff is, a large window opens up and displays everything in an organized manner.
I have been using this method for one day now and it works just fine. When I can't remember if I have something or what quantity I have, I just stand my Glitchen against the wall of junk and press the up arrow.