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.

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

Session Buddy - Manage Your Browser Sessions

Workona - A better way to work in the browser.

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

Tab Manager Plus for Chrome - The only tab manager you'll ever need