That's exactly what I feel: Some menu items are a little misplaced; and just explaining will not make the users entirely comfortable.Although another paragraph in the User Manual might help to clarify things, I view that as less satisfactory than fixing the program nits.
The menu requires some clean up:
First, the names "Folder Groups" and "Custom Groups" are too similar; and the user may mix them up (that is, he will tend to open them both to look for what he wants, rather than unerringly land on the desired option directly.)
Secondly, a "folder group" is nothing but a set of bookmarks which are loaded in tabs of a folder pane. That is exact equivalent to a "bookmark folder" in tabbed browsers (e.g. IE7, Mozilla/Firefox). Therefore, it should be renamed as "tab set" (or equivalent) and moved to the Bookmarks menu. In other words, the "folder group" is not related to Customize menu at all.
Similarly, the "Custom group" does not belong to "Customize" menu: It should be moved to the View| Arrange by menus. This menu already has the "show in groups" menu. The "show in custom groups" menu should be listed right below it.
Probably Nikos put these menus in Customize menu because there are organize options. But if we follow the browsers' example, the Organize option should be put in the respective menus only.



