I note three inconsistencies where opening bookmarks from the sidebar does not follow the tabbed browsing preferences for "Open tabs instead of windows for middle-click or control-click of links in web page": 1. Middle-clicking on a sidebar bookmark has no effect whatsoever. 2. Control-(left-)clicking on a bookmark has the standard Windows multiple-select behavior, but also loads the selected bookmark in the current tab. 3. When right-clicking on a bookmark, the context menu should have "Open in new tab" as an option in addition to "Open" and "Open in new window" -- or if context-menu bloat is a concern, perhaps in place of the "...new window" option according to a preference in the Tabbed Browsing area. This was observed on build 2002070808.
1. is bug 72361 2. is also part of bug 72361 (assuming you were expecting it to open in a new window or tab) 3. is a dup of bug 117449 (by way of bug 122215) duping to the first one... *** This bug has been marked as a duplicate of 72361 ***