After you hover the cursor over the particular section in the presentation, the „+” sign in the circle will appear below. You can create a new section or choose from the presets.
Detailed description:
Click the „+” sign in the circle that will appear at the bottom of the section when you hover the cursor over it
When clicked, the „Choose From Presets” section will appear at the top of the right toolbar under the „Add New Section”
Choose one of the presets from „Choose From Presets” (Cover, Title, Text Blocks, Gallery, Features)