If you have a maven project, recognized from NetBeans because of the pom.xml, NetBeans should create the folder nbproject anyway.
Why? There is a plugin called "NetBeans signer": http://plugins.netbeans.org/plugin/9499/netbeans-signer. You have to choose the NetBeans module folder. I did this, but if there is no nbproject folder, I got this message: `Project does NOT contain a NetBeans module.`.
I think this is not the part of the plugin, because it will create a keystore file right inside the nbproject/private folder, which is not there. I didn't test the CLI for creating a keystore file so I can't say smth about that.
If the nbproject/private folder not needed, then I will create a ticket for this plugin.