BTreeFolder2 is a Zope product that acts like a Zope folder but can
store many more items.

When you fill a Zope folder with too many items, both Zope and your
browser get overwhelmed.  Zope has to load and store a large folder
object, and the browser has to render large HTML tables repeatedly.
Zope can store a lot of objects, but it has trouble storing a lot of
objects in a single standard folder.