Add Cells, Columns, and Rows to the Layout Grid

To add more cells to the layout grid, click these buttons on the vertical toolbar.
Button
Action
insert column before cell icon
inserts a column to the left of the selected column
insert column after cell icon
inserts a column to the right of the selected column
add row before icon
adds a row above the selected row
add row after icon
adds a row below the selected row
split cell vertically icon
splits a selected cell vertically
split cell horizontal icon
splits a selected cell horizontally