:)

Thanks for the suggestions -- I didn't even know about the layout panel.  Entering a fraczerothick and entering a square bracket while the cursor is within the scope of both the upper and lower bound also looks perfect:

I appear to have found some kind of problem with VerticalBar and VerticalLine however.  Editing any text to the right of a VerticalBar or VerticalLine in the superscript position (by entering a ^) causes the worksheet row to grow for no apparent reason.  This happens even when using Backspace or Delete to remove characters from the superscript.

That's unfortunate -- it seems to be such a common expression.  Perhaps future versions will incorporate this notation.