Toy rotation has been such a great accidental find for fostering emotional skills - my little one learns appreciation and awareness while also developing her capacity for empathy as she often donates some of her older toys to charity.
She's at an age where she's becoming more aware of the world around her, so it's a great lesson on how to appreciate what you have and giving back - which is so heartwarming to see! We started with offering her choices of two baskets of toys - one out and one 'resting' and slowly graduated to three. It also meant that when visitors came over, she was more likely to share her toys
I think the key to making it work is having distinct storage spaces/bins for the 'resting' toys so they're not just dumped together - it makes the process of swapping them easier and more appealing. Also important: involving your little one in the process, making it a fun activity rather than a chore, which encourages them to engage with the purpose behind it too. We also have a 'special' box for absolute favourites that never go into rotation!
It's worked so well that we've extended it to books and art supplies too - so much less clutter and way more appreciation for each item!