That's just Mozilla completely killing any usability in their UI. Business as usual...
The icon no longer appears automatically. You have to click this silly puzzle piece button in your toolbar, scroll down to "Save Screenshot", click the gear icon, there and choose "Pin to Toolbar". Mozilla has been told by many users in several Bug reports that this needs improvement, but Mozilla doesn't care...

For hotkeys, you have to use the Mozilla built-in hotkey editor. In "about:addons", click the upper right "gear icon" and choose "Manage Extension Shortcuts".

And in future, please ask your questions on GitHub. Thanks.