After upgrading to Xfce 4.10 from 4.8, I noticed that the clock/notification area no longer pushed to the right edge of the panel.
This is due to a change in the Window Buttons panel plugin which no longer expands to fill the available space[1].
To emulate the old behavior, add a transparent separator between the window buttons and the clock/notification area, setting its expand property.
Voilla!
In the last screenshot it looks like the window buttons panel doesn’t expand anymore into the empty space and it cuts the terminal program button in half… Doesn’t look like it’s fixed (instead this is worse)…
Work well!!
Thanks!!!