The invocation option 'In a drop down' lets you expand and collapse the html code in the topic.
Invocation option 'In a drop down'
When the topic is shown in the browser, the html code is by default hidden.
Html code included in a topic
When you click the hotspot, the html code is shown. When you click the hotspot again, the html code becomes hidden once more. A drop down typically pushes the paragraphs after the hotspot downwards in the topic as indicated in the next image.
Html code shown in a drop down