Sidebery - Manage your tabs and bookmarks in sidebar.
Raindrop.io - All your articles, photos, video & content from web & apps in one place.
Tree Style Tab - Tree Style Tab is an all-in-one Firefox extension that provides ability in order to operate tabs as a tree.
Bookmark OS - Bookmark OS is like Mac or Windows optimized for bookmarks.
Firefox Multi-account Containers - Sign in to two different accounts on the same site
Toby - Better Than Bookmarks