It is accessible in the Tools menu in the Order Of Battle Editor.
In the menu click "Tools -> TC2M - SOWGB Converter -> Convert File", select a TC2M OOB File, click open, and it converts the file to SOWGB format, saves it, and then opens it in the editor.

I think this will save many many hours of time.

It is extendable (the sprite name replacements &c are in csv files) so it can be made to convert modded OOBs as well.