Rated 5 out of 5 stars

I can't use it because I'm not able to log in via google. I click on the "Continue with Google" button and a authentication tab opens in Firefox. After authenticating there a "Something went wrong" message appears. I guess the problem is that the authentication tab is opened in FF instead of Thunderbird...
Later edit: The developer answered that thunderbird does not allow opening a new tab (which is mandatory to happen when using social login) so I will change my rating since this is not a problem with the todoist extension but with thunderbird. Anyway, keep in mind that you'll not be able to use this extension if you authenticate on todoist via social accounts.

This tool is not suitable if you need to open a tab within an open tab as thunderbird does not allow this. You're welcome to contribute if you want through github.