To prevent user data loss when filling out forms, we’ve disabled the Backspace key as a navigation shortcut for the back navigation button. To re-enable the Backspace keyboard shortcut, you can change the about:config preference browser.backspace_action to 0. You can also use the recommended Alt + Left arrow (Command + Left arrow on Mac) shortcut instead. Firefox keyboard shortcuts
We've removed items from the Library menu that weren't used often or have other access points in the browser: Synced tabs, Recent highlights, and Pocket list.
We've simplified the Help menu by reducing redundant items, such as those that point to Firefox support pages that can also be accessed via the Get Help item.
In the image context menu, the "View Image Info” menu label has been removed.
We've greatly simplified the Web Developer menu. Go to Application Menu > Web Developer > Web Developer Tools to access Inspector, Web Console, Debugger, Network Style Error, Performance, Storage Inspector, Accessibility, and Application