If you try to remove a property group from a template, but that property group contains any properties that are still in use by a provisional specification, the property group will not be removed but will be marked as hidden instead.

Hidden property groups are not displayed in provisional specifications using the given tempate, but are visible in the Configure Provisional Specifications app for reference. If a hidden property group is changed back to visible by an administrator, the property group becomes again visible in the provisional specification with any previously stored property data.