While I was working on the rendered images of the various vanilla maps included with the game, I learned quite a bit about the file format, and therefore decided to develop a editing tool for it.
The tool is fairly basic in nature currently, but several maps have been released using the tool successfully. The interface itself should be fairly easy to use, and documentation for it is coming soon.
If you do make something cool with this, please feel free to share the tool around!
Double clicking the executable will give you a GUI interface, simple as that.
If you want more advanced tools, invoking it as
java -jar EscapistsEditor-1.0.exe --help
(yes, that is a .exe) will give you command-line access to some utilities.
Feel free to tweak your map in the editor and, when completed, save it to a easy-to-access location. These can be pasted over the maps located at Data\Maps in the Escapists install directory for Stream (etc: C:\Program Files (x86)\Steam\steamapps\common\The Escapists\Data\Maps), but make BACKUPS first!
The editor does require Java 1.8.