In this case, they could simply connect to the SAME Google Drive from Gmail.
The notes of each other will be displayed in the history section.
2. For each member, connect to that account.
3. Now, when user A write some notes in the email titled ‘hi’
4. User B, could see the note in the same email thread.
5. When user B put down the notes, user A could see it too.
6. If SGN history is not shown, please make sure that 'Show Note History(No effect for Inbox)' is checked in preference section.