Note/reserved designation for squares

[MatthewCline]

There should be some way to put a note on a square that you want to reserve for some future use, so you don't accidentally use it for something else.  Once you put a note on a square, clicking on it would let you edit the text for the note, change the color of the note symbol, and maybe even change the note symbol; hovering over the block would give a tooltip containing the text of the note.  Attempting to dig or construct on a square with a note would fail with some sort of noise.  "Cancel" would be used to delete a note.

[ImpalerWrG]

I'd recommend a Notes view option with simple boxes created by dragging, then type and text appearing on the box, this would be a fine planning too indeed