There is a plugin template that ships with LabVIEW that you can use to get started writing your shortcut:
[LabVIEW 2012]\resource\dialog\QuickDrop\QuickDrop Plugin Template.vi
Yes, I know it should be a .vit file, and it will be in LabVIEW 2013...but for now, you have to save your own copy somewhere. Anyway, this VI is full of commentary describing how you go about adding the necessary scripting code for your plugin. The template already includes the bookend code necessary to set up an Undo transaction for whatever operation your plugin performs.
You can place your plugin VI in one of the following two locations to make it available as a QDKS:
[LabVIEW Data]\Quick Drop Plugins
If you put your plugin in the LabVIEW 20xx folder, it will only be available in that version of LabVIEW. If you put it in the LabVIEW Data folder, it will be available in any LabVIEW version (2010 and later), as long as you saved it in the earliest LabVIEW version you want to support.
Not sure how to get started actually writing the scripting code for your plugin? The shipping plugins are all fully documented, so you can browse their code for reference:
The Wire All Terminals and VI Server Rename plugins are password-protected because they use private scripting functionality, but the other plugins are available for your perusal. If you need any help writing your plugin, the Quick Drop Enthusiasts group on the NI Community has lots of experience writing shortcuts, and there are dozens of community shortcuts that you can use for reference as well.
Sharing your Shortcut
Once your plugin is ready for prime time, share it with the world! Post it to the Quick Drop Enthusiasts community, and include a link to it on the List of Community Quick Drop Keyboard Shortcuts page.