On macOS there are two ways to reference a Bear note from another note:
Linking using permanent URL
You can get link to the note by right clicking a note in the Note List, using the
Copy Link To Note menu item and pasting the Note Link in another note.
You can also copy a Note Link from the Information Pane.
On iOS you can access to the same functionality by sliding a note inside the Note List and tapping
Note Links can also be used to reference Bear notes from an external application.
Linking using title
Another way to create a note link is to write a note title between four square brackets. For example, if you have a note titled Apple pie recipe and you want to reference it inside another note, all you have to do is insert this text:
[[Apple pie recipe]]