The ••• (Page Actions) button is only shown when at least one of the actions is applicable to a page, so yes, that does move the "Show History" button to the left. I think you have several options, but all of them will require a little tinkering on your part. (1) Fix the width of the Page Actions area so whether it loads or not, the Show History button is always in the same place. This may waste space in the address bar, but you should see everything. (2) Hide the whole Page Actions area behind a hover button so you can call it up on demand but otherwise it's hidden. If you depend on seeing the bookmark star, this is less convenient than keeping it visible. Otherwise, it maximizes your address bar space. (3) Hide the ••• button until you hover over the Page Actions area. The Show History button still might move when the Reader View icon is added but it will be less common. (Or maybe that icon can be hidden, too.) Any of these would use a custom style rule that you apply to Firefox using a userChrome.css file. A mouthful, I realize, but a powerful tool to tweak the UI once you become familiar with it. I created a site about using userChrome.css, when you have a few minutes. Rules for #1-#3 aren't on there, but you can get a general idea: https://www.userchrome.org/what-is-userchrome-css.html