Hi Marko,
The Shorten URL API was revamped to make it store URLs that are capable of migrating versions.
In Kibana, applications register an object with the Locator Service. The object defines the locator ID, how to form a link from application state, and how to migrate application state from older versions.
When making a new short URL using the API, the best starting place will be to first create a short URL in the browser, while watching the network requests in the Network Inspector. These requests us the same API you can use in your scripts.
If you have the short URL saved in .kibana using a previous version, those URLs should be migrated after you upgrade to 7.16.1 -- but that could depend on which version you upgraded from. So you should have your previous short URLs available and you can use those as a starting point.