How to extend multiple extjs classes?

Hi,

I am trying to add more features to /libs/cq/ui/rte/core/commands/DefaultFormatting.js like shade, fontcolor, allcaps. In DefaultFormatting.js file it extends Command.js file by default.Here i'm trying to add a dialog to get user inputs like in TablePlugin.js file, but i'm getting this.editorKernal not defined because editorKernal available only in Plugin.js.

So to get access to editorKernal i need to extend Plugin.js in /libs/cq/ui/rte/core/commands/DefaultFormatting.js.

Any idea how we can call editorKernal? or how we can add a dialog to /libs/cq/ui/rte/core/commands/DefaultFormatting.js?

Thanks.

Vikram.