The add-on SDK attaches panels to widgets as seen here. I would like to achieve the same effect using the add-on SDK with a toolbar button instead.
The
You can create a Toolbarbutton and Panel using the Addon SDK and some Jetpack modules. Try toolbarwidget-jplib and browser-action-jplib by Rob--W.
You can easy add a button to the toolbar and style the panel whatever you want with css / html:
var badge = require('browserAction').BrowserAction({
default_icon: 'images/icon19.png', // optional
default_title: 'Badge title', // optional; shown in tooltip
default_popup: 'popup.html' // optional
});