Today's #FreeSoftwareAdvent are some extensions which I find particularly useful.
For Thunderbird:
* Quick Folder Move lets me file email (including into folders in different accounts) via the keyboard. I use this goodness knows how many tens of times a day. https://services.addons.thunderbird.net/en-US/thunderbird/addon/quick-folder-move/
For Firefox:
* Consent-o-matic automatically suppresses malicious compliance cookie banners: https://addons.mozilla.org/en-GB/firefox/addon/consent-o-matic/
* uBlock Origin blocks all sorts of problematic stuff, and helps make for a much nicer browsing experience: https://addons.mozilla.org/en-GB/firefox/addon/ublock-origin/
* Recipe Filter foregrounds the actual recipe on recipe pages: https://addons.mozilla.org/en-GB/firefox/addon/recipe-filter/
* Shut Up is a comments blocker, which makes the web far more pleasant, with fewer random people's opinions: https://addons.mozilla.org/en-GB/firefox/addon/shut-up-comment-blocker/