Here is an image depicting this approach. For an explanation of this approach, please scroll down after the image.
Image from: https://eiuwrites.blogspot.com/2015/10/making-organized-plan.html
You might have encountered formal outlines in high school where you use roman numberals, letters, etc. This notetaking method builds on outlining, but it's not that strict and has more flexibility and less detail than formal outlines.
You begin by writing the main points against the left margin of the page. Then, you indent and write supporting points and details below them. You can then indent again as the supporting points and details get more specific. So, you are organizing from broad ideas to specific ideas. When you review your notes later, you can number or highlight points to identify relationships.
Outline notes require active listening and thoughtful decisions when determining what to write down, but it allows you to record as much supporting detail as you need. Such notes are easiest when a class presentation is well organized and especially helpful when the instructor provides a brief outline, a handout, or PowerPoint slides. In discussion classes, question and answer sessions, or lectures that are not clearly organized, outline notetaking may be a bit challenging and you may need to use multiple pages in your notebook to organize the information, using a half-page or even a full page for each topic if the discussion surrounding the topic is robust.