Looking into map.txt of any mod's directory one can quickly recognize the structure of the map. E.g. the main defintions:
SIZE 120 120
FOGSIDES 1 2 3 4 5 6 7 8
0 GroundAnim\am10_out0000.bmp 3067 64
MUCHY_RECT 0 0 0 0
EAGLES 5 80
WATER_COLORS 404010 7 FFE0D0 3 FFE0D0
The map is 120x120 hexes, we start at "time zero", the player controls side 2 etc. etc.
Most of the things found in map.txt you can easily modify using the editor but some you can't. For instance the map Russian 09_cont map has the following lines in map.txt:
end_of_file 2 40 7 13 -1 F
end_of_file 2 64 38 13 -1 F
end_of_file 2 85 52 13 -1 F
end_of_file 2 101 51 13 -1 F
This defines areas of visibilities for side 2 at hexes [40,7], [64,38], [85,52] and [101,51] with a view distance of 13 hexes (normal view, not "radar mode"). You can make these kind of tricks yourself by saving your map e.g. after having planted a remote camera in a tree, but as far as I know there is no way of removing the thing afterwards (at least using the editor alone without going in-game, make some changes and then save). If one could just manually edit map.txt and make the editor accept the changes it would be easy to change things back (in this case: Remove the SEE_AREA block).
Just changing map.txt doesn't have any effect, probably because map.bin holds the same information as map.txt but in a different (compiled) format.
Removing map.bin renders the editor unable to open the map.
What apparently works (sometimes...) is to open the map in the editor, make and save the changes in map.txt, delete map.bin, restart the map, run the map, restart the map and finally save the map (creating a new map.bin based on your modified map.txt).