Line Numbers & Line Highlights
You can turn line numbers on or off in the block toolbar. When line numbers are enabled, you can optional specify which lines to highlight. This is useful when you want to emphasize specific lines that you'll be talking about. Line highlights are provided as a comma separated list of line numbers. For example:
"1,4,10" will highlight lines 1, 4 and 10.
"2,5-15" will highlight lines 2 and 5 through 15.