Rated 5 out of 5 stars

This is a wonderful addon. But, with the latest Windows 10 updates, the latest Thunderbird (78.9.1) and the latest BorderColors D (2021.4.1), I can no longer find a way to get to the BorderColors D settings. There is no line in Thunderbird's Tools menu for Addon Settings.

Hello there, glad to read that you find the add-on useful!

I'm not sure which Thunderbird version introduced the change, but most add-on options are now on the Add-ons tab. BorderColors-D doesn't do anything different, so they should appear there as well.

See this page for directions:
https://support.mozilla.org/en-US/kb/thunderbird-add-ons-frequently-asked-questions#w_how-do-i-configure-add-ons