For example, the expiry parameter to action=protect takes one expiry timestamp per protections, and it's entirely possible that someone would want to apply the same expiry to more than one protection. The API itself handles this fine, but the CapsuleMultiSelectWidget used in ApiSandbox does not allow this to be entered.

This will require a flag to OO.ui.CapsuleMultiSelectWidget to enable this behavior when it is needed.