Hi Scott,

1. We've implemented an experimental feature for ExtJS documentation moving forward that uses JSDuck (thanks to your recommendation). It's not available in production environments but you can access it by turning it on under "Admin Console" > "Experimental Features" > "JavaScript Documentation" in your local instance. When we do have public API wrapped for ExtJS 4+ components we will expose these docs publicly.

2. Currently, the classes found in internal/webapp/extWidgets are not considered part of our publicly supported API and as such I would not recommend using them for production environment apps.

In the case of the Ext4Store I'd recommend using our JavaScript Query API and populating data stores directly.

3. First, I'd recommend trying to use our dependency loading structure implemented in 12.2. See our documentation here. Second, the Ext.Loader will work you just have to ensure to configure it before use. See the Ext 4 docs on Ext.Loader.setConfig().

Thanks,
Nick