Screen off memo - how to add to an existing pinned memo?

[xxaarraa]

I have been using the pin note to lock screen feature recently to set reminders. How do I add / delete to an existing pinned memo? I can't seem to just write on the screen on the same memo, and when I go into the memo itself and add and save, the new additions don't appear on the lock screen.

Anyone know?

 

[xxaarraa]

Anyone?