I was tired loosing time using the mouse to switch between "to:" and "cc:" when adding mail adresses to the mail I was writing. Using this addon is no more needed, just use the ALT+CTRL+C keyboard shortcut!
Development discontinued. More info here
Documentation & support
Bugs
To send a bug report use github.
Future improvements
Check the issue tracker for planned features.
How does it work?
When you're writing an address in the composer window, just press ALT+CTRL+C to toggle between "cc:" and "to:", without using your mouse!
Image courtesy of "webdesignerdepot".