I found this official article. https://support.mozilla.org/en-US/kb/keyboard-shortcuts#w_customize-or-disable-keyboard-shortcuts 1) Since it's in the knowledge base, Mozilla confirms that it's a frequently-enough asked question. Why not build it into Thunderbird? After 78 versions, you would think they'd add some handy cool features, wouldn't you? 2) The two third-party addons being suggested don't work because they haven't been updated since Thunderbird 60-ish. Also, they are third-part, what was Mozilla thinking, suggesting an addon that they cannot guarantee is safe?! Anyway, I'm not asking what a good/working addon for Thunderbird would be to do this. I don't care, because ALL addons I've ever installed in Thunderbird become obsolute at some point, because the authors can't be bothered to keep up with Mozilla's ongoing crippling of third-party addons. That's why I want this fairly basic feature built into Thunderbird. It makes perfect sense to have this, given the very "keyboardy" nature of the app.