In Montessori principles the idea is to set toys up in open shelves that toddlers/children can help themselves to.
Toys should be undone, for example a puzzle should not be on the shelf all put together, the idea is to have everything undone so the child can try and accomplish putting the pieces of the puzzle or toy back together and also encourage open ended play (not one way to play with the toy). This allows the child to engage with the activity or toy and build concentration. Also kids get extremely bored of toys quickly, it's encouraged to not have all a child's toys out at once. Just by taking away a toy and replacing it with an old one will seem like a brand new toy to them.
I've left some favourites but just moved them around, usually placing the easiest first, and the more challenging ones as you go along the shelf. He can't reach the top shelf yet, that's all more for toy storage.