Sidebery - Manage your tabs and bookmarks in sidebar.
TreeCard - The wooden debit card that plants tree powered by Ecosia
Tree Style Tab - Tree Style Tab is an all-in-one Firefox extension that provides ability in order to operate tabs as a tree.
TreeMapper - TreeMapper is an easy-to-use tool for standardized on-site data collection on forest restoration.
Firefox Multi-account Containers - Sign in to two different accounts on the same site
Treeapp - Plant a tree for free, every day, in less than a minute