Trying to find the right question for my problem.

I can not figure out how to build an app with definitions (models, views, stores, controllers) that extend 3rd party/vendor library definitions. In my particular case, the vendor lib definitions are themselves extensions of Ext definitions.

I've added the vendor lib to my app.json's "js" paths, and have added the lib in my index.html.

And, the app runs, uncompiled, without error.

Does the Cmd v3 tool support compiling apps that use vendor libs like this?
If so, how? If not, is there a roadmap for support? And, what should I do in the mean-time?
Thank you for any hints whatsoever!