We can name lines rather than targeting them by number. Name the line inside brackets. In the code below you can see that I name the very first column line
col1-start then comes the 100 pixel first column track. Having named the lines you can use the names, rather than numbers.
You always have the line numbers to use - even if you name some or all of your lines.
See the Pen Grid by Example 7: Line-based placement named lines by rachelandrew (@rachelandrew) on CodePen.