UMS maps are built with community tools rather than Blizzard's own editor. Three of them do the work, and they do different jobs.
- ScmDraft 2 - terrain, unit placement, locations, unit names. This is the tool that owns the .scx file.
- TrigEditPlus - edits classic triggers as text. Far faster than ScmDraft's trigger window, and it is also the form you can later hand to a model.
- EUD Editor 3 - where EPScript goes and where the map is compiled. Everything you will have a model write in this course ends up here, so treat it as required.
Open the same map in two tools and save from both, and one tool's work disappears. Work in one at a time.
Make one working folder and keep the map and your exported text files in it. Put a backup of the original there too.