How to create sections with alternating between-row spacing?

You can create sections with alternating between-row spacing by layering two identical sections on top of one another, then adjusting the between-row spacing of each till they align to your spacing requirements. You can use the line tool as a de facto measuring tool to get the spacing just right.

For example, if I wanted to plant chestnuts in rows with alternating 12 ft x 18 ft x 12 ft x 18 ft spacing, I would adhere to the following steps:

Create your first section, assign the chestnut template to this section, then adjust between-row spacing to 30 ft under Geometry in your Design panel.
Then, use the Line tool (via the "New Section" button) to measure out a 12 ft offset from your first section's rows. You can view the exact measurement of your line in the Inspect panel, under row ft. This measurement will help guide you in placing your next section's rows.
Create another identical section layered directly on top of the original section, assign it the chestnut template. Change its between-row spacing to 30 ft, then use the Offset tool to align this section's rows to the 12 ft offset measured out in step 2.
You should now have 12 x 18 ft spacing mapped out for your combined sections. You may need to adjust each section's angle using the Rotate tool so the rows are parallel.