The map editor does not open a previously created map.

Here's a tip from the Winner that I think is quite good. As I understand it, he meant that even if the map file is corrupted, we still have "temporary" files created by the editor in the Editor/H5MMods/[map name] folder. We copy them from there and archive them into a zip file. Then, we put the archive into the maps folder and rename it to .h5m, and that's it!