You are able to leave a note about a patient without anyone other than practice admins to see. By going into their patient chart and clicking into the notes section. 

You can flag a note by pressing on the flag button to the right of the note (see image above). This will flag the patient as a whole- the blue flag icon will show to the right of their name and will be visible from the main patient page. To remove the flag, simply press "unflag".