The Rectangle with indvidually editable corners - Yes!

[angelize]

This is a workaround and it can be a bit fiddly but if you have a version of Xara capable of opacity masks then yes you can create a rectangle and edit the corners indvidually! I was also able to copy an editable rectangle group from DP7 and paste it into WD7Premium.

note: in the video when I show moving the fills I held shift and marquee selected the fill handles with the fill tools active and was able to move them together,after releasing shift.