While navigating through windows explorer I can click "back" button on my mouse or in the toolbar to navigate back to the previous location.
Now when I'm navigating through bookmarks in Opera I often hit "back" out of habituation and are then brought back to the speeddial page or if BM-manager was opened in a new tab, nothing happens.
Since bookmarks are either opened in a new tab or you're going there from speeddial, most often there is no previous website one might want to go back to. Thus I'd love to have backward/forward -commands to navigate through bookmarks.

Also, what about accessing bookmark folders via direct url in the style of opera://bookmarks/path_to/desired_folder/.
This could make it possible to set direct links to often used folders to speeddial or bm-bar and make forward/backward navigation possible. (There are some use-cases where this might be nice to have)

Another suggestion would be to provide an opt-in at bm-manager to "Show this folder in speed-dial". This way users can store collections of bookmarks in one place (bm-manager) and just link to these folders from speed-dial. This might solve the problem of same speeddial icons for pages from the same domain.