There is not a keyboard shortcut to launch the icon editor that I know of. You could potentially write a Quick Drop Keyboard Shortcut to accomplish this.
This page describes how to create a Quick Drop Keyboard Shortcut:
As for the actual scripting code in your plugin, here's some code that uses the LabVIEW Icon API to launch the icon editor and update the icon of a VI:
To learn more about the LabVIEW Icon API, and other really cool "unofficial" APIs in LabVIEW, check out http://www.ni.com/hiddengems .