There’s no short ID natively in Asana; the only available unique task ID is the ID that you can get from the browser address bar or the “Copy task link” button. The link looks something like this:
https://app.asana.com/0/883576482920561/1200441936770903/f
and the task ID is the last number (in this example, 1200441936770903).
If you want a true short ID, our Flowsana integration provides this capability; you can read more about it here.