How to link notes in macOS Notes application?
If you click on the “Add People” button in the top right corner, it will take you to a version of the iOS Share Sheet. Choose “Copy Link” and then select “Copy Link” again in the top right corner.  

It will upload the note to your iCloud and give you a URL. Still trying to figure out how to get the “ID” from the link to use mobilenotes:// (since that would be easier).