**Context**

Needed for ##54751.

**Acceptance criteria**

Begin of the insertionThere is a component which can be used inside a Primer::Beta::BorderBox

End of the insertion * Begin of the insertionIt accepts

End of the insertion Begin of the deletion Is collapsible/expandable

End of the deletion * Begin of the insertiontitle (e.g. "Backlogs")

* End of the insertion Begin of the deletion CanEnd of the deletion optionally Begin of the deletion haveEnd of the deletion a counter after the Begin of the insertiontitle (e.g. "BacklogsEnd of the insertion Begin of the deletion label ("BacklogsEnd of the deletion (6)") Begin of the insertion

* optionally a description displayed below the title

* Next to the counter (or title if there is no counter) there is a chevronEnd of the insertion

* Begin of the insertionThe component is clickable to extend/collapse the whole BorderBox

* End of the insertion When collapsed, the bottom border is thicker (2px) to indicate there are items hidden Begin of the insertion

End of the insertion Begin of the deletion

End of the deletion * Click zone to expand/collapse is the label set, consisting of: Begin of the insertion

End of the insertion Begin of the deletion

End of the deletion * Label Begin of the insertion

End of the insertion Begin of the deletion

End of the deletion * Counter (optional) Begin of the insertion

End of the insertion Begin of the deletion

End of the deletion * Arrow Begin of the insertion


End of the insertion Begin of the deletion

* Can still have a more action on the right edge


End of the deletion **Figma**

* _To be designed_


**Technical notes**

* Primer repo


**Out of scope**

* Begin of the insertionA whole `CollapsibleBorderBox` component

* to make it easier to re-use the collapsible meachnism later

* to make it easier that all BorderBoxes on the page look the same (with additional elements in the header as dragDrop icon, ActionMenu, etc)End of the insertion Begin of the deletion <br>End of the deletion