I'm using the latest stable Firefox 30.0. I'm bothered by the big round Back button and the wide address bar that goes with it.
I would like it to change it to a lean Back button (just a rectangle) and a thin address bar.
The usual advice is to right-click the toolbar, click Customize and enable "Use small icons". But Firefox redesigned the browser customization recently and the new look doesn't have this option.
I'm open to installing add-ons to solve this, but a browser-only solution gets priority.
Note: I'm not looking for rectangular tabs.
My main intention in asking this was to reclaim the wasted space from the wide address bar. I like the Australis look, and I don't mind having it (with the round Back button). For this reason, I picked Australis Small Icons over the Classic Theme Restorer.