How to convert XML to JSON:
- Open expansions.json
- Set the "pointer" to an XML file
- Run a Minecraft world, MAtmos enabled
- The expansion will be generated in:
.minecraft/mods/matmos/expansions_r27_userconfig/DO NOT EDIT UNLESS COPIED/...
- Copy the contents of this folder somewhere else;
  The contents are overwritten each start
- Continue from here by changing the pointer to a json file