Switched to this after SuperStop ironically stopped working. Togglific works well with one caveat: Please add an option to disable the "Animation Paused!/Resumed!" notifications. I find them obtrusive and unnecessary.

Update: this extension doesn't seem to work on the macOS (Big Sur, MacBook Pro Retina, 13-inch, Mid 2014) version of Firefox 138.0.4. At least the button doesn't appear on the toolbar. I can't figure out how to make the button available.

Update 2: the keyboard shortcut works: Shift-Command-X but the button is missing.