Hi @haibmf,
You are correct that we have recently changed how custom apps are created, and how the access tokens for custom apps are retrieved.
Previously merchant created custom apps were created in the Store’s Admin directly, with the access token and credentials displayed in the app settings in the admin as well.
Now that we’ve added the Dev Dashboard, all apps are created and managed in the Dev Dashboard directly, both Partner and Merchant created custom apps included.
For custom apps created in the Dev Dashboard, you will now need to use one of the available authentication methods to retrieve the access token, this won’t be displayed directly in the settings anymore to ensure app and store security.
The easiest way to retrieve the access token is with the Client Credential Grant method.
To do this you will need to retrieve the Client ID and Client Secret for the app, from the Dev Dashboard. Then you need to make an HTTP POST Request to https://{shop_name}.myshopify.com/admin/oauth/access_token, passing the client_id, client_secret, and grant_type parameters in the request body (for grant_type you will always pass the value as client_credentials)
Then once you make the HTTP POST Request, Shopify will respond to the request with the access token, the scopes that the token is eligible for, and when the token expires.
Here’s also some documentation on the other Authentication Methods that you can use instead of the Client Credential Grant.