Rated 5 out of 5 stars
Worked great on Thunderbird 20 on Windows 7/64 bit. Finally, I was able to enter the code and create a button to load the Activity Manager in a new tab instead of a window.
It was also easy to create a button to load the start page, which I have as a local-disk, graphics file. Add new button > Name "Start Page" > Paste Code > loadStartPage(); > Get Button Icon From Disk > DONE! Too cool!