Review for Header Tools Lite by Ferryman
Rated 5 out of 5 stars
This add-on is a must for me, absolutely fantastic, it helps to keep my mails organized.
Unfortunately, "Change header details" option does not work anymore in TB v31.4. "Edit full source" does, but it's a bit more dangerous if you only want to change mail subject.
To create your own collections, you must have a Mozilla Add-ons account.