Menu items should be able to have tooltips (if that isn't already the case), especially for the bookmarks menu, the personal toolbar folder menus and the site navigation bar menus. Their tooltips should be the URLs the menu items refer to - just like the "normal" bookmarks / site navigation links do have such kinds of tooltips.
related: bug 23460 <.02c> tooltips in menus are irritating since they tend to obscure other menu items </.02c>
True, but they're useful, and if a bookmark in first layer (e.g. those without menus, but directly visible in Personal Toolbar) has a context menu, a bookmark in further layers should have that too.
*** This bug has been marked as a duplicate of 62683 ***
I don't think this is a dupe of bug 62683 as that one talks about bookmarks while this one about the general ability of menu items to have tooltips. This bug's description does mention the bookmarks menu, but only as an example of the use of this feature. This may or may not be WONTFIX, but not a dupe of bug 62683. See also related bug 47434 which requests statusbar tips for menuitems. I think some kind of additional description of menu items is sometimes needed, either in the statusbar or in a tooltip or both. See bug 65121 comment 92 for an example (of course, it's just an idea that will probably be rejected).