Using darktable to tag photos, it allows nested tags, for instance Country|County|Town, dopus displays in wrong order as Town;Country;County.
Tags added using the Windows properties dialogs appear in the same order in Opus, so I'd say the issue may be with the tool you're using, not Opus.
Sounds like darktable relies on xmp sidecar files to support its hierarchical tags. That's probably beyond what simple file tags can offer.
https://docs.darktable.org/usermanual/3.6/module-reference/utility-modules/shared/tagging