The ability to drive unconstrained repeating metadata
Essentially, this is allowing the ability to add metadata not necessarily from a drop down list.
Adminrwijangco (Admin, Box) commented
This is common in traditional ECM platforms. For insurance customers, a common example might be the need to add multiple policy numbers to a document as metadata. It would NOT make sense to have a drop down of ALL policy numbers to choose from since there would potentially be millions.