I'm trying to find a way to do this also.
I don't think it's possible :/
I think you're looking for the ScriptTag API https://help.shopify.com/en/api/reference/online-store/scripttag
Make sure to use order_status as the display_scope.
Cool I'll give it a test. Not sure if it will work though because I'm looking to use liquid as well, this seems like it will add a 3rd party script rather than allow the same liquid / JS embed as you can do in the Additional scripts area.
Thanks I didn't know about this one 👍