The App Feedback plugin is not supported in the current version of Cordova Developer App, but we will try to add the support in the next version.
To use the App Feedback at the moment you will need to build and deploy the application on the device.
Telerik by Progress
Do you want to have your say when we set our development plans?
Do you want to know when a feature you care about is added or when a bug fixed?
Telerik Feedback Portal
and vote to affect the priority of the items