Hello,
As a workaround, you can flip the image of the sizing grip in right to left mode:
(TryCast(Me.radPopupEditor1.PopupForm, RadSizablePopupControl)).SizingGrip.GripItemNSEW.Image.RotateFlipType = RotateFlipType.RotateNoneFlipX
Regards,
Todor Vyagov
Progress Telerik