A very comfortable feature of BibSonomy is available again in Version 3, an easy way to edit tags without having to edit the whole entry. Whenever looking at your own entries in some way you can use the "edit tags button" shown in the picture below to change the tags of this entry.
The following window will appear. New tags can be added by typing the tag followed by a space bar. Just don't forget to hit the save button!
You can also edit tags of multiple entries which is desribed in another FotW.