Note only

Well, actually this is not possible in FlexR, there always is a Shift required , but there is a solution that comes pretty close:

To achieve this, create a shift without name an with default 00:00 (12:00AM) times.
Use this 'empty' shift in the calendar to add your non-shift related appointment and use the Note field to add your appointment info.
It's even possible to use the Shift time and notification when you actually plan it in the FlexR calendar.