This is most often called the “disclosure view” or “disclosure panel” and usually should have an intelligent container appearance (which grows / shrinks / scrolls correctly with several expandable disclosure areas). There is no such control in the API. Most developers roll back their own, while some use third-party open source.
Omni Frameworks have one such control that works very well (including tear-off panels, etc., if I remember correctly). Disadvantage: this is a large structure and has many other things in it.
InspectorKit is different. It is more focused (only the control itself and the IB module), but the last incarnation I tested had several problems with the user interface with the Interface Builder plugin.
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