Nice find!
I am working on the editor each and every day, currently toiling away at the save map feature (Hundreds of byte adresses need to be filled
) After that come proper editing tools like copying, cutting and pasting cells, filters (hiding water indicators, for example), auxiliary (monster, items, eggs) browser...
BTW, I found out that the map editor (the "proper" one), when saving a map, calculates the lighting completely wrong. Basically, if a cell is to be lit (by sky or ceiling leight), a certain bit flag is set in the map data file for that cell. However, the editor just fills all cells, even if there are no lights anywhere and the whole map consists of solid blocks. Curiously, only floors get lit, and not walls.
The AGA version also has a strange way of rendering the horizon; Depending on where the character stands outside and which direction he or she faces, a second, different horizon in lighter color (lighter than black) is drawn in front of the proper one. I have not found out how exactly makes this happen.