Notes as an overlay instead of separate Mode?

[mnalis]

Notes, as currently implemented in 2.0 (in #47) leave something to be desired. While I understand they are to be a part of "Walking papers mode", there are several problems with using them effectively, e.g.:

• Do not hide existing Notes when creating new Note #460
• Show notes locations on the map chooser panel #459
• [Request] Keep zoom levels persistent across modes #230

Which makes me wonder: would it be more sensible to make Notes a toggle-able overlay in other modes, instead of being a separate mode in itself?

e.g. when in Micromapping, Amenity or Entrance modes, clicking a Show/Hide notes button would display or hide Notes in that same mode? (there should be a toggle instead of displaying Notes permanently, or otherwise Notes would often hide amenities below them)