There is also a menu adding into the tools menu for accessing the same functionality, but it can be hidden if you don't want it.
Since WebExtensions (Firefox 57+) don't support multiple buttons per extension look at these extensions to replace this one: Go to Top of Page,
Scroll One Page Up, Scroll One Page Down and
Go to Bottom of Page
The extension is part of the Toolbar Buttons project and is built with the MozButton SDK. Follow us on Twitter, or get involved on GitHub.
If you have ideas for new features we are more then happy to consider them for the next release. Just leave a comment, or better post to our Forums