By default, add-on toolbar icons are stored in the Extensions button (looks like a puzzle piece) on the toolbar. This is to stop add-ons from cluttering up your browser. You can pin some extensions to the toolbar by pressing the Gear icon next to the add-on and selecting "Pin to Toolbar". However, not every add-on can be pinned to the toolbar. It depends on what functionality the add-on developer has built into the add-on. For more information, please refer to the [[Manage your extensions using the extensions button in the toolbar]] article. Hope this helps.