The changelog for 0.10.0 lists:
Z-Wave JS: Allow specifying RF region for OTA firmware updates if the region is unknown or cannot be queried
But there is no setting that enables this functionality in the add-on configuration UI. I’m doing this as a feature request, rather than opening a ticket here, because, technically, this is not a bug, but it feels like one, since this is a feature being touted that is inaccessible.