The very idea of the Favorites Folder, as once implemented, has been jettisoned by everyone, including Microsoft, with any contemporary browser. The new Chromium-based Edge does what all other browsers do - maintain Favorites/Bookmarks internally to the browser, though one can export and import them.
CTRL+D is pretty much the universal, "Bookmark this page," command and works in Firefox as well as all Chromium-based browsers. In any Chromium based browser CTRL+Shift+O opens the Bookmarks/Favorites Manager, which is, I find, the easiest way to locate and/or organize one's bookmarks to one's own satisfaction. Under Firefox the CTRL+Shift+B command opens the bookmarks manager.
Brian - Windows 10 Pro, 64-Bit, Version 1909, Build 18363
Tolerance is the positive and cordial effort to understand another's beliefs, practices, and habits without necessarily sharing or accepting them.
~ Joshua Liebman