Hide or collapse a container in 'Sort items in multiple containers'

[mabusdogma]

First of all thank you for this new feature, it works well in a project about travels, specially in binary options like visited/non visited countries.

There's something I would like to propose as an improvement (if it's not already done): a way to hide or collapse one container in 'Sort items in multiple containers'.

Let's imagine 95% of the time you just need to change the order of a few items in Container A (a lot like 'Sort items in a single container'), but 5% of the time you need to change an item, from a big pool of unused... let's say 50 or 100 items to choose in Container B. Maybe you would like to hide or collapse this huge (and most of the time useless) container B until you need it, and then hide it again.

For now I use normal multiselect boxes in this scenario, because there's no enough space for a big Container B but it would be amazing to use streamlit sortables with drag and drop, combined with a reduction of space when Container B is not needed.

Cheers!