app/pb_kits/playbook/pb_collapsible/docs/_collapsible_icons

Prop

The icon prop allows you to customize your icon sets by passing it an array of any comma-separated pair of icon values. The first icon value will replace the kit’s default icon when collapsed (chevron-down), and the second value will replace the default icon when expanded (chevron-up). icon also allows you to pass it a single icon as a string, in which case the icon will not toggle with the collapsible state.