To delete collections:

Control-click the name of the collection you want to remove in the Collection list.

Choose Delete from the pop-up menu.
If you change your mind, choose Edit > Undo.
You can delete any of the collections in your Collections list.
Control-click the name of the collection you want to remove in the Collection list.
Choose Delete from the pop-up menu.
If you change your mind, choose Edit > Undo.
The All Bookmarks collection can not be deleted.
If you’re deleting a collection that contains other collections you must first remove the containing collections.