Session Buddy - Manage Your Browser Sessions

Tree Style Tab - Tree Style Tab is an all-in-one Firefox extension that provides ability in order to operate tabs as a tree.

OneTab - Whenever you find yourself with too many tabs, click the OneTab icon to convert all of your tabs into a list. When you need to access the tabs again, you can either restore them individually or all at once.

Session Box - Using websites with multiple accounts at the same time is made easy.

Firefox Multi-account Containers - Sign in to two different accounts on the same site

Bulk URL Tool - With the Bulk URL Tool web application you can open up to 200 URLs all at once effortlessly.