By creating a user, you can specify the language of the chat dialog for each user and limit the LINE official accounts that can be used.
See "Creating a user" for more information on users.
You can switch the language of the chat dialog by specifying the language in the user settings.
You can also limit the LINE official accounts that can be switched in the chat dialog by specifying the use account.
Please note that if you create a user and do not specify any LINE OA account, the user will not be able to select any LINE official account in the chat dialog.
Next: About Mobile chat app