How to deploy Admin block extension to Store

[nhtbao101]

I'm following the docs of Admin block extension to custom the UI of Admin customer detail, I can preview this app but can't deploy this app to my store.
When I run the deploy command:

npm run deploy

I got an error: 

extensions.targeting: Block extension is in developer preview and cannot be deployed to production stores.

I checked the docs and it says: "Admin blocks are in developer preview and can't be deployed to production versions of your app."
So I have a confused: If I cannot deploy this app to my store, how can I add and customize the UI of admin in production environment. If cannot, is another way to customize the Admin UI?

Any suggestions or recommendation?
Thanks in advance.