TL;DR
1
Add Dividers with the + Icon
Hover over an open field, click the + icon, select Divider.
2
Add with the / shortcut
Press / on your keyboard, type Divider, and select it.
Let's Do It Together!
1. Add Divider via Plus Icon
Hover over the open field in your Doc.
Click the + icon.
Scroll down and select Divider.
2. Add Divider via / Command
Press the / key in the open field.
Type Divider and select it.
