Firefox Add-on which exports all cookies to a Netscape HTTP Cookie File, as used by curl, wget, and youtube-dl, among others. Available at https://addons.mozilla.org/en-US/firefox/addon/cookies-txt/.
This addon adds an icon to the toolbar, which can be used to toggle a popup menu:
The Add-on is able to export the cookies for each of the containers in Firefox. The cookies of the default container will be exported in cookies.txt, the cookies of any other named container will be exported in cookies.*name-of-container*.txt.