You should be able to customize built-in toolbar buttons like the Home button in customize mode from the palette panel to the toolbar or move them around, but buttons added by an extension behave differently. In Firefox 87+ the Library and the Home button aren't present by default on the Navigation Toolbar and you need to drag them out of the Customize palette to the toolbar. *https://support.mozilla.org/en-US/kb/customize-firefox-controls-buttons-and-toolbars Firefox 109 comes with the Extensions button in the Navigation Toolbar as the new way to manage your extensions. The panel that opens if you click the Extensions button (puzzle piece icon) serves as overflow area for extensions you install. The legacy chevron (>>) overflow area still exists but is only used for built-in toolbar buttons as found in the [/kb/customize-firefox-controls-buttons-and-toolbars Customize page]. In the Extensions button panel, you can click the gear icon [[Image:Fx91GearIcon|width=20]] next to an extension or use the right-click context menu to pin the extension to the toolbar (Pin to Toolbar). To (re)move the extension from the toolbar back to the Extensions button panel, you can use "Unpin from Toolbar" in the right-click context menu. More Information: *https://support.mozilla.org/en-US/kb/extensions-button