Strongly suggest that since there is the intent to keep the 2 *columns* as
separate entities, implying individual calculations and/or data, "Center
Across Selection" is the *preferred* method, instead of "Merge Cells".
<Format> <Cells> <Alignment> tab,
Expand the "Horizontal" window, and select,
"CenterAcrossSelection", <OK>.
Merge Cells will create various problems when the individual columns are to
be "worked" on; (i.e ... try sorting them).