When you create evergreens, it’s important to fill permanent notes with links to other notes to create interconnections, which are the most important asset you build when you use a note-writing system. The most important links are those between permanent notes and structure notes. Whenever you write permanent notes about what you read to test understanding, or for other purposes, connect the permanent note to a structure note, which can also be under a bigger structure note. This step makes sure that an individual note is connected to the biggest possible network of related notes. You can also do this when you create iterative outlines as you write notes.
References
Fast, S. (100 C.E., 54:00). Introduction to the Zettelkasten Method. Zettelkasten Method. https://www.zettelkasten.de/introduction/