Favorite the bookmark first
Only favorited bookmarks can be added to Speed Dial. Open the bookmark's actions, mark it as a favorite, then add it to your Speed Dial choices.
Hidden content is removed from Speed Dial
If you hide a bookmark, the Chest that contains it, or its Cave, CoW automatically removes that bookmark from Speed Dial. This prevents private links from appearing in quick-access areas. Reveal the content again before adding the bookmark back to Speed Dial.