ever so often I want to have info in the schematic that should not visible persistently, like current consumptions, calibration voltages… you get the idea. This info tends to clutter a schematic.
So sort of overlay layers would be a charm. I know, I know: this is a schematic editor, no art editor etc. etc. Anyways…
EDIT. For a few projects I have resorted to a second schematic sheet to explain the design to myself. It saves those WTF moments a year later when I try to remember why I took a certain approach to whatever in a design. An overlay with the notes would be a lot easier and more convenient.