I can’t find option or method or what ever, to make new address inside existing wallet, for my app wich I am making in Node.js.
I’m not sure how to do it. Probably address is created based on main account private key.
You can look at nanowallet source code: https://github.com/NemProject/NanoWallet/
You can also try ask on Telegram @nemprojects channel. There is more developers available there.