How can I restore 'History' to the toolbar after mistakenly moving it to the application menu?

I'm not sure what you mean. Can you give more detail? Is this about a toolbar button you (re)moved accidentally? *https://support.mozilla.org/en-US/kb/customize-firefox-controls-buttons-and-toolbars Can you attach a screenshot? *https://support.mozilla.org/en-US/kb/how-do-i-create-screenshot-my-problem *use a compressed image type like PNG or JPG to save the screenshot

If you mean the top menu bar (File, Edit, View, History, Bookmarks, Tools, Help), this article has the steps to bring it back: [[Restore the Menu bar in Firefox]].