You can create links between your notes using the following:
Just type the current title of a regular note into any other note with double square brackets and it turns into a link. If the note title does not exist, it will create a new note with that title after you click on it. If you change the title of the note after linking, NotePlan will update the title in every linked note automatically.
The title of a note is always the first line of the text inside a note.
You can also link calendar notes by using the date in the following way:
[[YYYY-MM-DD]], for example
Linked notes appear in the references area at the top of the target note: