I am working on a table for my employer and would like to add a complete percentage display for each row. Is there a formula that I would use on the last row that would calculate the percentage complete based on how many columns contain data?

I am not aware of a formula that will do that in a table. But if it is ok to show the percentage filled on the canvas above the table, or anywhere else, you could do that relatively easily by writing a formula that filters and count the filled rows, and then also count all rows, and express that as a ratio.

(You could also put that formula in a column in the table, displaying the same value in every row.)

But you cannot have a row with a formula, only columns.