* each file has a descriptive name that starts with an iso date
* each file is on a specific topic or idea
* you are using a text editor/IDE like vscode that has good search tools
You can search a keyword across your whole notes database and you can see immediately when the note was written to get some chronological context and see, of course, the note itself. You can scroll through the list of results to see other places where you're using that keyword.
The visual graph part the author is using is just a toy.
TLDR: any full-text-search notes database is functionally a Zettelkasten, don't stress about it, just start taking notes