Pressing the extension’s button loads home page (domain root) of the currently viewed site. The extension’s options also allow to switch to opening the extension’s menu by pressing the button.
The extension button’s menu contains a list of hierarchical parts of the current page’s URL with ability to go to any of corresponding parent pages, and other useful items:
“Remove query string”, “Remove hash (anchor)”, “Canonical URL”, “Minimal URL”, “Search in Internet Archive”, “Copy” submenu, “Open in private window”, “Delete the page from history”, “Forget the site”, “Browser’s start page” (Firefox 58+).
Android note: availability of all features of the extension in Firefox for Android is not tested and not guaranteed.