What you see in the picture is the content of a Grid cell. The 12 individual items (6Label, 6 TextBox) are painfully placed by hand and therefore they keep on getting messed at design time, plus their behavior at run time is not the best.
I began to study the different types of layout containers and have considered 2 alternatives:
(1) A UniformGrid. The problem is that I don't know whether that container supports uniformity of rows while lack of symmetry in columns.
(2) Two Stacks, side by side. They probably would have to be inside some outside container, maybe a 1-row x 2-columnGrid?
Thanks for your comments and observations....