The mm7/8 files are slightly different (but not greatly different) from the mm6 files. Before some of the more detailed decoding was done, the editor worked for both.

I'll figure out how the mm7/8 stuff is different once I have something mostly working for mm6.

The indoor maps will be something I'll probably get working this month, but I still have some things to decode for the outdoor maps.

As for coordinates, the center of the map is 0,0.
I think west and south are negative.

"reachable" parts of the map are from 45056 to -45056.
Parts of the map beyond on that are viewable, but you can't move to them in game.

You can use the pixel and text maps to get a general idea of where things are.

I'm open to ideas on how to make it easier to figure out coordinates, but I'm not yet to the point where I'm ready to provide a 3d view from the editor.

I've made a lot of changes, and I'll probably release a new version of the editor this week, maybe even tonight.