loaded http://api.openstreetmap.org/api/0.6/relation/448030/12 , saved it as file.
Opened in an editor and added a action=“modify” in the header and changed the Version number to the current one. Loaded the file in JOSM and uploaded it.
done
Do you need your new relation ?
I can save version 13 in a new relation if you want.
Matthias