Because there needs to be a complete audit trail of Medical Notes, the software does not allow deletion.
Medical Notes can be edited in a way to hide them from the Medical History tooltip.
All iterations of a Medical Note (full history) can be viewed by means of the Show Audit option in the Medical tab.
Hiding a Medical Note from Medical History Tooltip
It is not possible to delete a Medical Note, but you can hide it from the Medical History tooltip.
To hide a Medical Note from the Medical History Tooltip
Select the Note.
Click the Edit (e|d) button .
Replace the Note text contents with either a dash "-" or the word "ERASED", and press Enter.
This note will then normally not be visible in the Medical History Tooltip, but will be visible in the Medical tab:
All of its historical iterations will be visible in the Medical tab when you check (tick) the Show Audit checkbox: