In Numbers, how can I determine the default formatting of cells in rows that have just been added to a sheet?
I found the following tutorial at Apple that has the answer to my own question: The default table styles are always taken from the table style list that you choose from the panel on the bottom-left corner of the screen. 

The solution to my problem is to use the Create New Table Style command under the Format menu and adding a brand new table style. As long as this new style remains selected, it is the one that the table will keep as a whole. 

I have tried this at home and it works as advertised.