Sorry, I don't see how accessing add-ons relates to bookmarks, so I'm guessing what you want answered.

{ Ctrl + Shft + A } to open the Add-ons tab

Hit the 3-bar button on the right-side of Navigation bar to see the Toolbar buttons that are in the Menu Panel.

Use Customize in the Menu Panel to find Toolbar buttons that aren't in the Menu Panel or on a Toolbar.

What you could do is take the icons you don't use often, and move them to a secondary toolbar. Use the options to keep it hidden until it's needed.

Note that you can right-click a toolbar button and click "Move to Menu" to move this button to the "3-bar" Firefox menu button drop-down list if you do not want or need it on the Navigation Toolbar.

You can look at the Classic Theme Restorer extension to restore some functionality that was lost with the arrival of the Australis style in Firefox 29.

• Classic Theme Restorer: https://addons.mozilla.org/firefox/addon/classicthemerestorer/

• You can check out the settings of the CTR extension via its Options/Preferences button on the "Firefox/Tools > Add-ons > Extensions" page.
• You can find extra toolbar buttons and more toolbar settings in Customize (3-bar Firefox menu button > Customize)

See also:

• https://support.mozilla.org/kb/how-to-make-new-firefox-look-like-old-firefox
• https://support.mozilla.org/kb/common-questions-after-updating-to-new-firefox
• https://support.mozilla.org/kb/learn-more-about-the-design-of-new-firefox