Not sure why you'd want to slow down a section by putting the brakes on. ;-)
The closest analogy to a section break in Numbers would be to place the new 'section' in a separate table. If you already have the table built, you can easily tear off the bottom row. Separated from the original table, it will become a single row table of its own. Any formulas in that row will be automatically adjusted to refere to the correct row, and, if necessary to the now separate 'other' table.
To tear one or more rows fom a table, select the row(s), then use the mouse to grab one of the row header tabs and drag it right and down until it separates from the rest of the table. When the dragged rows are completely separate from the original table, release the mouse button to drop the row(s) and form a new table. Then move that table to where you want it.