I have seen some Webi users try to add a table footer by trying to insert a new row below the last row of the table, however; this will not work as it will create one row for every existing row on the table and will completely perplex the table. A second approach that I’ve seen users adopt is creating a new table with only one row beneath the last row of the table as the footer, but this approach is also troublesome as the footer would be a phantom row and it may intertwine and overlap with the main table if new data is added to the main table. Here is the correct way for creating a table footer in Webi.
Select the table. Then go to “Report Element” > "Table Layout" > “Footer” > “Show Table Footer”
A footer row is correctly added.
Now, this field could be added for adding data such as subtotals.