If you want to open a folder of bookmarks in tabs, Firefox normally replaces all of your current tabs—but reader Raghav writes in with a quick configuration trick to fix that behaviour.
To make Firefox append the new tabs to the ones you already have open, you'll want to head over to about:config, filter for the browser.tabs.LoadFolderAndReplace key, and then double-click on it to change the value to false. The change should take effect immediately, no restarting needed.
For more, check out some of Raghav's other submitted tips: You can slow down the scroll speed, use the scroll wheel to zip through browser history, middle-click to open links in a new foreground tab, or even make Win+E open the folder of your choice. Thanks, Raghav!