The sidebar can be seen when an admin clicks an appointment in the diary.
It gives the admin useful information on the patient and the appointment without having to leave the diary and enter the appointment view page. From the sidebar, admins can reschedule the appointment, view the appointment show screen, take payment for the appointment, or create new invoices.
To turn on this feature, first, click settings, then System & account and then Admin accounts. Click the options and then edit button (to the right of the individual's name) to reach the below screen.
Scroll down to toggle the diary sidebar on or off, and click save.