This feature was not implemented by the Wikidata / WIkibase team and is not maintained by the team either.
It was introduced in T184000: Magic word on English WP to override display of Wikidata short description and even then it probably should not have been added to Wikibase.git
Right now I would propose that this be moved to some extension controlled and owned by whichever WMF team owns this feature, OR to a package within Wikibase.git that has clearly defined owners.
Quickly looking through the code it would appear that this would be:
- definition of 2 magic words
- 2 config settings
- localization messages
- The API implementation Wikibase\Client\Api\Description
- A hook handler Wikibase\Client\Hooks\DescriptionProviderHookHandler
- The parser function handler Wikibase\Client\Hooks\ShortDescHandler
- UsageLookup for the feature
And it may also require a new hook or extension mechanism for this usage related bit.