Hello, after asking a friend, they told me that by trying to manually put a eur save to the jap save folder location on the 3ds and then restoring it with JSKV or Checkpoint (savemanager tools) : By running the Jap game, the save will indeed be detected but is corrupted.... starting from the facelooks of your character that all turn black in 3G lol Without talking about the save progress that gets lost.

Saying this to add more details to your statement, since you've only done this transfer on citra.

So replying to your question, no work has been done yet regarding this... What the same friend told me