Transfer customizations

Yes, I have Two Site named Test and Demo on a Single Bench named ERPNext in my Linux Server on Contabo - CPU 2Core, 4GB Ram, 300GB HDD, Unlimited Bandwith.

Custom APP mytest >> Salary Slip Customization in Core Doctype
bench --site my.example.com install-app mytest

Custom APP mydemo >> Supplier Registration custom Doctype
bench --site test.example.com install-app mydemo

Another Help is Here. Thanks to @abbas for sharing a Helpfull Thread.