The red box in the figure below is the navigation toolbar, which contains the address bar and some of the tool buttons on the browser.
Firefox browser allows you to customize your toolbars, including the display in the browser, add or remove additional tool buttons, rearrange button locations, and so on to meet your needs:
Move your mouse around the toolbar, right-click, and pop-up small menu bar
Select the Customize button to eject the Custom toolbars window below. You can add and remove tool buttons from the toolbar by dragging or dragging the tool buttons, and you can sort the tool buttons according to your own habits. When you have finished making changes, click Finish to close the Custom toolbar window.
At the bottom of the Custom toolbar window, there are other options for changing the appearance of the toolbar:
Display: From the drop-down shown, you can choose to display it in the toolbar: icon, text or icon and text together. By default, the display icon of the Firefox browser.
Use small icons: to save screen space on the toolbar, you can choose to use small icons.