Version: 3.4.1 (using KDE 4.4.3) OS: Linux Installed from: Archlinux Packages Open "Settings/File renamer configuration". Select "artist", "genre" or "year" category and try to add it to the list: nothing happens.
I'm pretty sure this bug has already been fixed (bug 118317) but perhaps this is something else. Either way I can't reproduce here. :-/
This issue was fixed by a kind JuK debugger (Giorgos Kylafas), the fix will be released as part of the KDE 4.6.3 software compilation. See SVN commit 1228556 or 1228555 for more details.
Missed the fixed-in tag, sorry.
*** Bug 264090 has been marked as a duplicate of this bug. ***