Hey 76mm. The game comes with a mapmaker app (for making maps), a scenmaker app (for making or altering scenarios) and an estab editor (for creating forces, OOBs, units). All have fairly easy to grasp manuals, but you do need to study them and experiment. I haven't done any estab editing (making units, armies etc) and I gather that's the hardest of the 3 to grasp. I have tinkered at length with scenarios and its very easy to do. I've made a few maps and that's great fun and only slightly harder.
There were a fair few mods (maps, scenarios, OOBs) when the game was CO1, over at Matrix, but it's still new as CO2 right now and still getting up steam, I think. Caphillrat is about to produce an EF map, estab (the OOB for both sides) and scenario. You can look at his blog to get the idea of what kind of thing can be done. The Sharp End Gaming. Just as an example.
http://thesharpendgaming.blogspot.fi/
I also started an 'article' in the articles section of this site using the scenario and map of Prokhorovka that I made. Just as another example. That's here:
http://forums.lnlpublishing.com/xz-articles/kursk-comops-1-aar-part-1.8/
Peter
There doesn't seem to be a modding sub forum or such like. No. And, in fact, there aren't really any mods, as such, produced. You can't mess with the code. You can make maps, make armies and make scenarios for them.