I add new layout for my keyboard by using keyboard layout settings dialog in Xfce. Then i logout and login again. But xkb plugin can not change the current keyboard layout in Xfce 4.6.1 (by clicking on the flag icon or by pressing Alt+Shift key, neither of them works!). This problem (or bug) is just related to Xfce 4.6.1 (not Xfce 4.6). There is two way to solve the problem temporary: 1) I go to the keyboard layout settings dialog again and close it without any change, then xkb plugin will work very well and i can change current keyboard layout easily. But if i logout and login again, then the problem will be coming back and i must to do the mentioned solution again and again (on every time that i login) 2) I edit xorg.conf file and add new layout for my keyboard with options such as "grp:alt_shift_toggle". If i do it, then there is no need to do it again for each login. :-) Therefore it's a better solution than first way. Thank you...
Created attachment 4640 screenshot of xkb and preferences dialog with different data. Confirm for xfce 4.8
Confirm for xfce 4.8