Collapsible array field

[Laruxo]

I have an array field that is automatically generated and can contain hundreds of items. It would be nice to make this field collapsible. Currently, it is possible to do this by wrapping it in a fieldset or creating a custom field component with a local state. Both solutions have some drawbacks.

It seems this should be easily doable in Sanity core, there is even a TODO:

sanity/packages/sanity/src/core/form/store/formState.ts

Line 446 in f0c94f1

// todo: consider support for collapsible arrays

Additional context
Previous issue: #722