A cool third use for Rainbow Stones would've been..

[vurt]

...to use them to predict a jump, since platforming isn't that great and kind of.. unprecise. It can be one of the more frustrating parts of the game.

I know you can drop them to see if you survive a fall or not. But you can't drop a stone to predict that's where you will land exactly. Like if you need to land on something specifically, they won't help you with that.

Throwing them to predict a jump would be super helpful too sometimes. Like if you throw them from where you stand they would land on the same spot as you would if you jump. Long press to lay down, short press to throw perhaps.

Sad to see they don't have a suggestion sub forum btw. there are many small tweaks that could've made the game even better.