When the current Planbook selection does not have a lesson that occurs on a given day, click the Add New Lesson button below the date to add a new lesson on that day.

If there is a neighboring unit to the day you’re adding the new lesson, you can specify whether the new lesson should occur in the neighboring unit or if it should be added as a standalone lesson outside of the unit.

Selecting the option "Make this the last lesson in ‘Unit 1’" places Lesson 2 in Unit 1 as shown in the Timeline image below.

Selecting the option "Add this lesson after ‘Unit 1’" places Lesson 2 following Unit 1 without a unit as shown in the Timeline image below.