The mission editor seems to be able to create an XML mission file correctly,
meaning added nodes are saved in the XML, but it’s not possible to reload it
back, the node editor is always blank, always starting from a blank file.
You need to set up the assetgroup correctly. You need to place the .xml in a
folder with the same name:
PackageSources\Missions\mission-name\mission-name.xml
For the AssetGroup, set the name to the same name as the .xml and point the
AssetDir to the new folder.
Thank you, it worked. I guess the problem is the project wizard, which is not
enforcing that naming convention when adding an asset of the Mission kind,
making you assume you could name the .xml mission source as you like.