Detach option not appearing in pool manager (needed to promote a spare)

According to this ticket, the device "Detach" feature of the legacy UI made it into the new UI but neither 11.3-U2 nor 11.3-U3.2 appear to have it:

https://jira.ixsystems.com/browse/NAS-102699

Caleb reports that the logic is there, but it is not appering in the UI.

This feature is important, unintuitive as it is, for promoting spare disks.

Related: A true "promote spare" would be nice.