To open the note, do one of the following:
If you shared the note: two-factor authentication enabled and iCloud Keychain turned on in System Settings can see others’ changes immediately, and color-coded triangles show where others are working in the note. See on your Mac.
Click the shared note, then swipe right with two fingers anywhere in the note.
You can also click in the toolbar.
Click Show All Activity.
Click a name in Activity view to see the changes the person made highlighted in the note.