Persisting data between checkout steps


How can we share additional data on checkout pages.
I want to save data in /checkout/cart page and display it on /checkout/confirm page.
I’ve tried with custom collector class which implements CartProcessorInterface and override process method.
I’ve tried save data (into Cart or SalesChannelContext), but it doesn’t work.

Is the only solution to use a symfony session? Foot-in-Mouth