Well, I think I can't make it clearer... In the first screen I go to BookmarksMenu, then the menu opens and I go on selecting Audio and Music subfolder: all the single bookmarks show up (second screenshot). But if I select Lyrics subfolder it looks like it's empty, but it's not (third screenshot). I have no clue why some subfolders show their contents and some does not. The number of bookmarks inside is irrelevant.
All bookmarks and subfolders show up just fine in the sidebar with the shortcut ⌃⌘1
What I'd like is a Bookmark menu just like Safari's and not Firefox, Opera etc. I understand this may be not feasible, I'm just saying that Orion present bookmark menu is cumbersome imho.