To leave notes in a conversation, click on All Inbox or a specific Inbox that you may have saved. Go to the message that you want to leave a note for. Click on the 'Note’ option (from the bottom text box) that you’ll see next to ‘Reply’.
Once you click on ‘Note’ the text box will change its color to indicate that you’re in the Notes mode.
You can start typing the note and add emojis to make your note more expressive.
Once you’ve composed your note, simply click on the ‘Add Note’ button from the bottom right to save the note.