shopify checkout ui extension

[zuhair1]

hello, I am trying to add some customize items on checkout page using shopify custom ui extension. but app is building and installing and also I created extension via command and now on running the app its not displaying on the dev store checkout customization page., although I also have access to shopify plus stores but on creating extension it wont showing on the stores list only dev stores are listed . Is there any other way to customize the chec