CoMET is the Crimson Fields Map Editing Tool. Please keep in mind that
this is still a work in progress (and much more so than the game itself).
Currently, the editor is considered to be in alpha state.

Most basic features are implemented. You can, for example, create new
maps, load, edit and save them, so it can already be a great help when
designing missions. One of the major limitations is that you can only
create single-line messages in plain ASCII. As a result, CoMET is for
now only really useful when used together with cfed, which it will
eventually replace. You can do the map layout with CoMET, export the
result as a text file, and add the missing bits by hand (see the cfed
documentation for details on how to do this).

CoMET can read the binary level files created with cfed, and you can make
modifications to them. Even settings not yet supported by CoMET should
remain intact during this procedure.