This article describes how to go from a standard table...
...to a table with an additional column that sums all the values in that row:
A table with multiple columns.
1. Select your table.
2. Go to Properties > RULES on the object inspector.
3. To apply the rule, select the Plus (+) > Browse Online Library > Table Computations > Naive Total For Each Row.
4. Change the New row label as required.
5. Press OK.
This rule then adds a new column to the right of the table which contains a total for each row. The total is calculated by adding up all of the statistic values in that row, and excludes any columns that are duplicates of other columns in the table (e.g. NETs).
Note, if you select Switch rows and columns on your table, the rule will no longer work due to the table dimensions changing. In this case, you will have to apply the Naive Total For Each Column rule instead.