There are cases where you might want to package plugins with your app in your version control; like for example you are using a commercial plugin or maybe a proplugin and need to use cloud building.
The simplest setup that I have personally used is in the very root of your application.
You create a folder called plugins. Inside this folder you put any commercial and plugins you need to keep with the apps source. For example one of my projects looks like the above picture, I have 5 plugins that are actually in version control with the application. So anyone checking out the source code from git will get all these plugins with the application.
To use these plugins in your NativeScript app, in the root directory you type "tns plugin add ./plugins/nativescript-compress-0.0.1.tgz" you need to type the ENTIRE name including the extension.
How do I download them
So say I want to have the proplugins/nativescript-dialog plugin.
npm pack @proplugins/nativescript-dialog
will download the latest .tgz file into the current directory for you.