Fixed bars like this infest sooo many websites, cluttering the view and restricting how much of the content you can see at once, and ad blockers usually don't remove them. This extension lets you get rid of them quickly. Minor issue: I have to click the toolbar button twice before it works.

I have been looking for such an extension for a long time because fixed position elements in mobile browser is a worse problem due to the small screen size. Unfortunately, while I can install this extension in Firefox Android there is no way to get it working.