Hi @Aziz ,
For Pay-As-You-Go subscriptions, the Advanced Management Portal has migrated to Manage DNS Records to provide an Azure portal centric experience. If your domain is being managed by Azure i.e. you bought the domain inside the portal, then you can leverage the Manage DNS Records blade to make any updates. If your domain is not managed by Azure, then you can either migrate the domain into Azure or transfer it so you can adjust records in a different registrar. Have a look at Managing an App Service Domain for more information.
If your subscription is not pay as you go, then you need to be the owner of the subscription, not just the resource group. If you're not an owner of the subscription, then the Global Admin can create a custom role that has Microsoft.DomainRegistration/generateSSOAction/action at the subscription level access to your account. Do note, that the link to open the feature may be under Domain Management of the App Service Domain toolbar.