Short answer is no.

You want more. Have you read the relevant support article that describes each permission that can be requested and what it means. https://mzl.la/3JIWMwr

In this case. This add-on has been around for many years without any sort of issues except finding a new maintainer when the infrastructure it ran on changed and the original authors were no longer available to maintain the code. The add-on is developed on github and all of the code it uses is open source and publicly available https://github.com/TB-throwback/LookOut-fix-version so any attempt to send data anywhere in the code that is not allowed can be seen by anyone that cares to look. One of the issues with open source is it is very hard to have security, or broken security, through obscurity. Many proprietary programs rely on the closed nature of their code to hide many of their less admirable activities like data collection and selling. With open source you have folk looking over your shoulder all the time to see you are doing it right!

All add-ons that get loaded to the addons.thunderbird.net web site are reviewed by the Thunderbird add-on reviewers before they are made public, so malfeasance is really quite unlikely, but I think the article answers your questions about how things can be opened to third parties. Given that largely the add-on is written by a third party. THey could manage to slip something trough. Unlikely but possible I guess.

Dear Matt, Thank you very much for your thorough answer. I am completely calm now.