It is version 1, and pre-alpha, so there are many issues and it is not the best, but there is support for it and does many things better than the unofficial editor.
This is a UI mod, you can play multiplayer without your opponents having it too.
This is the first guide for the new official Supreme Commander Map Editor. It is very graphical, with plenty of pictures so that you can understand map editing and making more easily.
Included in the file are scripts for an application (also included) to import custom models into Supreme Commander.
This is an unofficial Scenario Editor for the game Supreme Commander. This tools is just an early version and doesn't include all planned features yet.
SupComCP can tweak your SupCom and manage all of your data like Mods, Savegames, Replays and Maps.