Sorry, in order to attach a screenshot, you may need to reply to your question. (Yes, that is on the list to be fixed if it hasn't been fixed by now.)

I don't get a Library button if I right-click any toolbar. To open the Bookmark Organizer, you can use Ctrl+Shift+B, or press Alt+b to display the classic Bookmarks menu and choose Show All Bookmarks.

Do those work?

Or you can click the Bookmarks item in the Firefox menu button drop down list if the menu bar is hidden.

• https://support.mozilla.org/kb/how-do-i-use-bookmarks