Rated 5 out of 5 stars

I'm giving this a "provisional" 5-star rating. The provisional status is because the E hotkey appears non-functional. I am in 78.6 and it does not work. I went to the developer's GitHub site and also see many complaints there regarding this issue. Please add a Hot Key! How about using Ctrl-H which was the one that worked fine on the Add On this is replacing, namely HeaderTools Lite?

On the good side, this Add On does just what it says it will. I was waiting to move toTBird 78 until I had a replacement for HeadTools Lite and this is it. I prefer running it with its default option of making only local changes disabled. That is easy to do with a click on the Add On page. I find this a necessary tool for TBird. I'm surprised it is native to the program.

Thank you for creating this Add On. I like it so much I have already made a contribution as the developer has asked.

This review is for a previous version of the add-on (4.3). 

Rated 3 out of 5 stars

This is easy to use and works great, except as it says it works on only the local database. So unlike HeaderToolsLite that changes the actual header subject, the changes here will not show up on other devices you may have that are also running Thunderbird. So if I change a subject for an email in my inbox it only shows up that way on my local machine.

My wishes are that the actual email would be edited instead of just the local database and that this add-on be updated for Thunderbird 68. The ability to edit header subjects is very important to my use of Thunderbird and because v68 has broken this for existing add ons I am currently choosing to stay with v60.

This review is for a previous version of the add-on (2.1.1). 

The add-on is now compatible with TB68 as well. In the options you can select, if you want local database storage or global storage (via IMAP) of the modified subject.